enable GLib threading

Call g_thread_init() from main() to enable the GLib features which
make it thread safe.

configure.ac

@@ -274,7 +274,7 @@ AC_CHECK_LIB(nsl,gethostbyname,MPD_LIBS="$MPD_LIBS -lnsl",)
 AC_CHECK_LIB(m,exp,MPD_LIBS="$MPD_LIBS -lm",)
 AC_CHECK_FUNCS(setenv)
 
-PKG_CHECK_MODULES([GLIB], [glib-2.0 >= 2.4],,
+PKG_CHECK_MODULES([GLIB], [glib-2.0 >= 2.4 gthread-2.0],,
 		  [AC_MSG_ERROR([glib-2.4 is required])])
 
 dnl doesn't work for systems that don't have CODESET like OpenBSD

src/main.c

@@ -382,6 +382,9 @@ int main(int argc, char *argv[])
 	Options options;
 	clock_t start;
 
+	/* enable GLib's thread safety code */
+	g_thread_init(NULL);
+
 	initConf();
 
 	parseOptions(argc, argv, &options);