fix in commit today using strnlen, which is only available for gcc.

This adds a BLI_strnlen() to the blenlib.

Patch provided by Sergey Sharybin (nazgul)

source/blender/blenlib/intern/BLI_dynstr.c

@@ -85,7 +85,7 @@ void BLI_dynstr_append(DynStr *ds, const char *cstr) {
 
 void BLI_dynstr_nappend(DynStr *ds, const char *cstr, int len) {
 	DynStrElem *dse= malloc(sizeof(*dse));
-	int cstrlen= strnlen(cstr, len);
+	int cstrlen= BLI_strnlen(cstr, len);
 
 	dse->str= malloc(cstrlen+1);
 	memcpy(dse->str, cstr, cstrlen);

source/blender/blenlib/intern/string.c

@@ -342,3 +342,10 @@ void BLI_timestr(double _time, char *str)
 	
 	str[11]=0;
 }
+
+/* determine the length of a fixed-size string */
+size_t BLI_strnlen(const char *str, size_t maxlen)
+{
+	const char *end = memchr(str, '\0', maxlen);
+	return end ? (size_t) (end - str) : maxlen;
+}