avstring: Mark some character handling functions av_const

Signed-off-by: Martin Storsjö <martin@martin.st>

libavutil/avstring.h

@@ -154,22 +154,22 @@ char *av_get_token(const char **buf, const char *term);
 /**
  * Locale-independent conversion of ASCII isdigit.
  */
-int av_isdigit(int c);
+av_const int av_isdigit(int c);
 
 /**
  * Locale-independent conversion of ASCII isgraph.
  */
-int av_isgraph(int c);
+av_const int av_isgraph(int c);
 
 /**
  * Locale-independent conversion of ASCII isspace.
  */
-int av_isspace(int c);
+av_const int av_isspace(int c);
 
 /**
  * Locale-independent conversion of ASCII characters to uppercase.
  */
-static inline int av_toupper(int c)
+static inline av_const int av_toupper(int c)
 {
     if (c >= 'a' && c <= 'z')
         c ^= 0x20;
@@ -179,7 +179,7 @@ static inline int av_toupper(int c)
 /**
  * Locale-independent conversion of ASCII characters to lowercase.
  */
-static inline int av_tolower(int c)
+static inline av_const int av_tolower(int c)
 {
     if (c >= 'A' && c <= 'Z')
         c ^= 0x20;
@@ -189,7 +189,7 @@ static inline int av_tolower(int c)
 /**
  * Locale-independent conversion of ASCII isxdigit.
  */
-int av_isxdigit(int c);
+av_const int av_isxdigit(int c);
 
 /*
  * Locale-independent case-insensitive compare.