dbctype.h: avoid the inline keyword for c89 compatibility

gcc and clang accept __inline__ in any mode, so use that where
available, and fall back to plain static functions on other c89
compilers.

Author: basavaraj-sm05

src/dbctype.h

@@ -8,28 +8,38 @@
    about ASCII ranges, so simple comparisons suffice. Bytes outside
    0-127 never match. */
 
-static inline int ascii_isdigit(char c) {
+/* c89 has no "inline" keyword. gcc and clang accept __inline__ in
+   any mode; otherwise fall back to plain static functions. */
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
+#define DBCTYPE_INLINE static inline
+#elif defined(__GNUC__)
+#define DBCTYPE_INLINE static __inline__
+#else
+#define DBCTYPE_INLINE static
+#endif
+
+DBCTYPE_INLINE int ascii_isdigit(char c) {
 	return c >= '0' && c <= '9';
 }
 
-static inline int ascii_isalpha(char c) {
+DBCTYPE_INLINE int ascii_isalpha(char c) {
 	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
 }
 
-static inline int ascii_isalnum(char c) {
+DBCTYPE_INLINE int ascii_isalnum(char c) {
 	return ascii_isalpha(c) || ascii_isdigit(c);
 }
 
-static inline int ascii_isspace(char c) {
+DBCTYPE_INLINE int ascii_isspace(char c) {
 	return c == ' ' || c == '\t' || c == '\n'
 		|| c == '\v' || c == '\f' || c == '\r';
 }
 
-static inline int ascii_isprint(char c) {
+DBCTYPE_INLINE int ascii_isprint(char c) {
 	return c >= 0x20 && c <= 0x7e;
 }
 
-static inline char ascii_tolower(char c) {
+DBCTYPE_INLINE char ascii_tolower(char c) {
 	if (c >= 'A' && c <= 'Z') {
 		return c + ('a' - 'A');
 	}