Reworked Toy_String as a union, enabled -Wpedantic

Toy now fits into the C spec.

Fixed #158

Addendum: MacOS test caught an error:

error: a function declaration without a prototype is deprecated in all versions of C

That took 3 attempts to fix correctly.

Addendum: 'No new line at the end of file' are you shitting me?

source/toy_value.c

@@ -451,4 +451,5 @@ const char* Toy_private_getValueTypeAsCString(Toy_ValueType type) {
 	}
 
 	return NULL;
-}
+}
+