Add gcc_diag.h header, for macros used to do fine-grained exceptions …

…to GCC warnings

src/gcc_diag.h

@@ -0,0 +1,20 @@
+/* GCC diagnostics control macros courtesy of:
+ *   http://dbp-consulting.com/tutorials/SuppressingGCCWarnings.html
+ */
+#if ((__GNUC__ * 100) + __GNUC_MINOR__) >= 402
+# define GCC_DIAG_STR(s) #s
+# define GCC_DIAG_JOINSTR(x,y) GCC_DIAG_STR(x ## y)
+# define GCC_DIAG_DO_PRAGMA(x) _Pragma (#x)
+# define GCC_DIAG_PRAGMA(x) GCC_DIAG_DO_PRAGMA(GCC diagnostic x)
+# if ((__GNUC__ * 100) + __GNUC_MINOR__) >= 406
+#  define GCC_DIAG_OFF(x) GCC_DIAG_PRAGMA(push) \
+                          GCC_DIAG_PRAGMA(ignored GCC_DIAG_JOINSTR(-W,x))
+#  define GCC_DIAG_ON(x)  GCC_DIAG_PRAGMA(pop)
+# else
+#  define GCC_DIAG_OFF(x) GCC_DIAG_PRAGMA(ignored GCC_DIAG_JOINSTR(-W,x))
+#  define GCC_DIAG_ON(x)  GCC_DIAG_PRAGMA(warning GCC_DIAG_JOINSTR(-W,x))
+# endif
+#else
+# define GCC_DIAG_OFF(x)
+# define GCC_DIAG_ON(x)
+#endif