Use config.h rather than passing all defs in CFLAGS

src/plugin_common/charset.c

@@ -25,6 +25,10 @@
 #include <string.h>
 #include <errno.h>
 
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
 #ifdef HAVE_ICONV
 #include <iconv.h>
 #endif