Refactor gettext init

Put the gettext init code in a macro and define it appropriately
depending on whether gettext is actually available or not.

src/gettext.h

-#ifdef GETTEXT_FOUND
-#ifdef USE_GETTEXT
+#if defined(GETTEXT_FOUND) && defined(USE_GETTEXT)
 #include <libintl.h>
 #else
 #define gettext(String) String
-#define bindtextdomain(domain, dir) /* */
-#define textdomain(domain) /* */
-#endif
-#else
-#define gettext(String) String
-#define bindtextdomain(domain, dir) /* */
-#define textdomain(domain) /* */
 #endif
 
 #define _(String) gettext(String)
 #define gettext_noop(String) String
 #define N_(String) gettext_noop (String)
 
+inline void init_gettext(const char *path) {
+#if USE_GETTEXT
+	setlocale(LC_MESSAGES, "");
+	bindtextdomain(PROJECT_NAME, path);
+	textdomain(PROJECT_NAME);
+#endif
+}
+
 inline wchar_t* chartowchar_t(const char *str)
 {
 	size_t l = strlen(str)+1;

src/main.cpp

@@ -1132,11 +1132,7 @@ int main(int argc, char *argv[])
 	// Create user data directory
 	fs::CreateDir(porting::path_userdata);
 
-#ifdef LC_MESSAGES
-	setlocale(LC_MESSAGES, "");
-	bindtextdomain(PROJECT_NAME, (porting::path_userdata+"/locale").c_str());
-	textdomain(PROJECT_NAME);
-#endif
+	init_gettext((porting::path_userdata+"/locale").c_str());
 
 	// Initialize debug streams
 #ifdef RUN_IN_PLACE