Fixed API naming convention

Anything prepended with TOY_API is 'public'.

Anything that starts with Toy_private_* shouldn't be touched.

source/toy_common.c

@@ -3,6 +3,6 @@
 //defined separately, as compilation can take several seconds, invalidating the comparisons of the given macros
 static const char* build = __DATE__ " " __TIME__ ", incomplete Toy v2.x";
 
-const char* Toy_private_version_build(void) {
+const char* Toy_private_versionBuild(void) {
 	return build;
 }