Fix all references to config.h

config.h is created in $(top_buildir)/config.h.
Let's make sure all CPPFLAGS add correct -Ipath includes,
and that all code includes the correct file.

Change-Id: Ie9ea38bb009bc715b01cde4d66d181f7bec2e7bd
diff --git a/src/gsm/gsm0411_utils.c b/src/gsm/gsm0411_utils.c
index ccefe54..c26cd82 100644
--- a/src/gsm/gsm0411_utils.c
+++ b/src/gsm/gsm0411_utils.c
@@ -27,7 +27,7 @@
  *
  */
 
-#include "../../config.h"
+#include "config.h"
 
 #include <time.h>
 #include <string.h>