add legacy header values.h

some programs (procps, babl) expect it, and it doesn't seem to
cause any harm to just add it.
it's small and straightforward.

since math.h also defines MAXFLOAT, we undef it in both places,
before defining it.

include/math.h

@@ -346,6 +346,7 @@ long double truncl(long double);
 
 
 #if defined(_XOPEN_SOURCE) || defined(_BSD_SOURCE)
+#undef  MAXFLOAT
 #define MAXFLOAT        3.40282347e+38F
 #endif
 

include/values.h

@@ -0,0 +1,39 @@
+#ifndef _VALUES_H
+#define _VALUES_H
+
+#include <limits.h>
+
+#define CHARBITS   (sizeof(char)   * 8)
+#define SHORTBITS  (sizeof(short)  * 8)
+#define INTBITS    (sizeof(int)    * 8)
+#define LONGBITS   (sizeof(long)   * 8)
+#define PTRBITS    (sizeof(char *) * 8)
+#define DOUBLEBITS (sizeof(double) * 8)
+#define FLOATBITS  (sizeof(float)  * 8)
+
+#define MINSHORT SHRT_MIN
+#define MININT   INT_MIN
+#define MINLONG  LONG_MIN
+
+#define MAXSHORT SHRT_MAX
+#define MAXINT   INT_MAX
+#define MAXLONG  LONG_MAX
+
+#define HIBITS   MINSHORT
+#define HIBITL   MINLONG
+
+#include <float.h>
+
+#define MAXDOUBLE DBL_MAX
+#undef  MAXFLOAT
+#define MAXFLOAT  FLT_MAX
+#define MINDOUBLE DBL_MIN
+#define MINFLOAT  FLT_MIN
+#define DMINEXP   DBL_MIN_EXP
+#define FMINEXP   FLT_MIN_EXP
+#define DMAXEXP   DBL_MAX_EXP
+#define FMAXEXP   FLT_MAX_EXP
+
+#define BITSPERBYTE CHAR_BIT
+
+#endif