fixed test failure caused by missing inline-function declarations on gcc5.

Author: kztanaka

libcob.h

@@ -37,6 +37,7 @@ extern "C" {
 #include <libcob/strings.h>
 #include <libcob/termio.h>
 #include <libcob/intrinsic.h>
+#include <libcob/codegen.h>
 
 #ifdef __cplusplus
 }

libcob/numeric.c

@@ -30,12 +30,10 @@
 /* Force symbol exports */
 #define	COB_LIB_EXPIMP
 
+#define	COB_LIB_INCLUDE
 #include "libcob.h"
 #include "coblocal.h"
 
-#define	COB_LIB_INCLUDE
-#include "codegen.h"
-
 #define DECIMAL_NAN	-128
 #define DECIMAL_CHECK(d1,d2) \
   if (unlikely(d1->scale == DECIMAL_NAN || d2->scale == DECIMAL_NAN)) { \