sub: rename sd_lavc_conv.c to lavc_conv.c

The previous commit turned sd_lavc_conv from a sd_driver to
free-standing functions. Do the rename to reflect this change
separately to avoid confusing git's content tracking. (Or did
git solve this, making separating renames and content changes
unnecessary?)

TOOLS/old-makefile

@@ -221,9 +221,9 @@ SOURCES = audio/audio.c \
           sub/dec_sub.c \
           sub/draw_bmp.c \
           sub/img_convert.c \
+          sub/lavc_conv.c \
           sub/osd.c \
           sub/sd_lavc.c \
-          sub/sd_lavc_conv.c \
           ta/ta.c \
           ta/ta_utils.c \
           ta/ta_talloc.c \

wscript_build.py

@@ -254,12 +254,12 @@ def build(ctx):
         ( "sub/dec_sub.c" ),
         ( "sub/draw_bmp.c" ),
         ( "sub/img_convert.c" ),
+        ( "sub/lavc_conv.c" ),
         ( "sub/osd.c" ),
         ( "sub/osd_dummy.c",                     "dummy-osd" ),
         ( "sub/osd_libass.c",                    "libass-osd" ),
         ( "sub/sd_ass.c",                        "libass" ),
         ( "sub/sd_lavc.c" ),
-        ( "sub/sd_lavc_conv.c" ),
 
         ## Video
         ( "video/csputils.c" ),