[c89stringutils/c89stringutils_string_extras{.h,.c}] WiP FreeBSD and OpenBSD support

Author: SamuelMarks

c89stringutils/c89stringutils_string_extras.c

@@ -33,6 +33,10 @@
 
 #else
 
+#ifdef ANY_BSD
+#define _vsnprintf vsnprintf
+#endif /* ANY_BSD */
+
 inline int snprintf(char *buffer, size_t count, const char *format, ...) {
   int result;
   va_list args;

c89stringutils/c89stringutils_string_extras.h

@@ -14,6 +14,7 @@
 #if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
     defined(__bsdi__) || defined(__DragonFly__) || defined(BSD)
 #define ANY_BSD
+#define __BSD_VISIBLE 1
 #endif
 
 #if defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || defined(__NT__)