avutil/common: Move everything inside inclusion guards

libavutil/common.h is a public header that provides generic math
functions whereas libavutil/intmath.h is a private header that contains
plattform-specific optimized versions of said math functions. common.h
includes intmath.h (when building the FFmpeg libraries) so that the
optimized versions are used for them.

This interdependency sometimes causes trouble: intmath.h once contained
an inlined ff_sqrt function that relied upon av_log2_16bit. In case there
was no optimized logarithm available on this plattform, intmath.h needed
to include common.h to get the generic implementation and this has been
done after the optimized versions (if any) have been provided so that
common.h used the optimized versions; it also needed to be done before
ff_sqrt. Yet when intmath.h was included from common.h and if an ordinary
inclusion guard was used by common.h, the #include "common.h" in intmath.h
was a no-op and therefore av_log2_16bit was still unknown at the end of
intmath.h (and also in ff_sqrt) if no optimized version was available.

Before a955b59658 this was solved by
duplicating the #ifndef av_log2_16bit check after the inclusion of
common.h in intmath.h; said commit instead moved these checks to the
end of common.h, outside the inclusion guards and made common.h include
itself to get these unguarded defines. This is still the current
state of affairs.

Yet this is unnecessary since 9734b8ba56
as said commit removed ff_sqrt as well as the #include "common.h" from
intmath.h. Therefore this commit moves everything inside the inclusion
guards and makes common.h not include itself.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavutil/common.h

@@ -115,8 +115,72 @@
 #   include "intmath.h"
 #endif
 
-/* Pull in unguarded fallback defines at the end of this file. */
-#include "common.h"
+#ifndef av_ceil_log2
+#   define av_ceil_log2     av_ceil_log2_c
+#endif
+#ifndef av_clip
+#   define av_clip          av_clip_c
+#endif
+#ifndef av_clip64
+#   define av_clip64        av_clip64_c
+#endif
+#ifndef av_clip_uint8
+#   define av_clip_uint8    av_clip_uint8_c
+#endif
+#ifndef av_clip_int8
+#   define av_clip_int8     av_clip_int8_c
+#endif
+#ifndef av_clip_uint16
+#   define av_clip_uint16   av_clip_uint16_c
+#endif
+#ifndef av_clip_int16
+#   define av_clip_int16    av_clip_int16_c
+#endif
+#ifndef av_clipl_int32
+#   define av_clipl_int32   av_clipl_int32_c
+#endif
+#ifndef av_clip_intp2
+#   define av_clip_intp2    av_clip_intp2_c
+#endif
+#ifndef av_clip_uintp2
+#   define av_clip_uintp2   av_clip_uintp2_c
+#endif
+#ifndef av_mod_uintp2
+#   define av_mod_uintp2    av_mod_uintp2_c
+#endif
+#ifndef av_sat_add32
+#   define av_sat_add32     av_sat_add32_c
+#endif
+#ifndef av_sat_dadd32
+#   define av_sat_dadd32    av_sat_dadd32_c
+#endif
+#ifndef av_sat_sub32
+#   define av_sat_sub32     av_sat_sub32_c
+#endif
+#ifndef av_sat_dsub32
+#   define av_sat_dsub32    av_sat_dsub32_c
+#endif
+#ifndef av_sat_add64
+#   define av_sat_add64     av_sat_add64_c
+#endif
+#ifndef av_sat_sub64
+#   define av_sat_sub64     av_sat_sub64_c
+#endif
+#ifndef av_clipf
+#   define av_clipf         av_clipf_c
+#endif
+#ifndef av_clipd
+#   define av_clipd         av_clipd_c
+#endif
+#ifndef av_popcount
+#   define av_popcount      av_popcount_c
+#endif
+#ifndef av_popcount64
+#   define av_popcount64    av_popcount64_c
+#endif
+#ifndef av_parity
+#   define av_parity        av_parity_c
+#endif
 
 #ifndef av_log2
 av_const int av_log2(unsigned v);
@@ -542,75 +606,3 @@ static av_always_inline av_const int av_parity_c(uint32_t v)
 #endif /* HAVE_AV_CONFIG_H */
 
 #endif /* AVUTIL_COMMON_H */
-
-/*
- * The following definitions are outside the multiple inclusion guard
- * to ensure they are immediately available in intmath.h.
- */
-
-#ifndef av_ceil_log2
-#   define av_ceil_log2     av_ceil_log2_c
-#endif
-#ifndef av_clip
-#   define av_clip          av_clip_c
-#endif
-#ifndef av_clip64
-#   define av_clip64        av_clip64_c
-#endif
-#ifndef av_clip_uint8
-#   define av_clip_uint8    av_clip_uint8_c
-#endif
-#ifndef av_clip_int8
-#   define av_clip_int8     av_clip_int8_c
-#endif
-#ifndef av_clip_uint16
-#   define av_clip_uint16   av_clip_uint16_c
-#endif
-#ifndef av_clip_int16
-#   define av_clip_int16    av_clip_int16_c
-#endif
-#ifndef av_clipl_int32
-#   define av_clipl_int32   av_clipl_int32_c
-#endif
-#ifndef av_clip_intp2
-#   define av_clip_intp2    av_clip_intp2_c
-#endif
-#ifndef av_clip_uintp2
-#   define av_clip_uintp2   av_clip_uintp2_c
-#endif
-#ifndef av_mod_uintp2
-#   define av_mod_uintp2    av_mod_uintp2_c
-#endif
-#ifndef av_sat_add32
-#   define av_sat_add32     av_sat_add32_c
-#endif
-#ifndef av_sat_dadd32
-#   define av_sat_dadd32    av_sat_dadd32_c
-#endif
-#ifndef av_sat_sub32
-#   define av_sat_sub32     av_sat_sub32_c
-#endif
-#ifndef av_sat_dsub32
-#   define av_sat_dsub32    av_sat_dsub32_c
-#endif
-#ifndef av_sat_add64
-#   define av_sat_add64     av_sat_add64_c
-#endif
-#ifndef av_sat_sub64
-#   define av_sat_sub64     av_sat_sub64_c
-#endif
-#ifndef av_clipf
-#   define av_clipf         av_clipf_c
-#endif
-#ifndef av_clipd
-#   define av_clipd         av_clipd_c
-#endif
-#ifndef av_popcount
-#   define av_popcount      av_popcount_c
-#endif
-#ifndef av_popcount64
-#   define av_popcount64    av_popcount64_c
-#endif
-#ifndef av_parity
-#   define av_parity        av_parity_c
-#endif