Avoid corrupting diagnostic state with _Pragma changes.

The macros for ICC and MSVC correctly push and pop the diagnostic
state of the compiler when disabling deprecation warnings. The
ones for clang/gcc should do the same. Without this, if a blanket
deprecation warning is applied to the code base it'll be flipped
back on incorrectly with FF_ENABLE_DEPRECATION_WARNINGS.

Signed-off-by: Dale Curtis <dalecurtis@chromium.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavutil/internal.h

@@ -81,8 +81,8 @@
 #        define FF_DISABLE_DEPRECATION_WARNINGS __pragma(warning(push)) __pragma(warning(disable:4996))
 #        define FF_ENABLE_DEPRECATION_WARNINGS  __pragma(warning(pop))
 #    else
-#        define FF_DISABLE_DEPRECATION_WARNINGS _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"")
-#        define FF_ENABLE_DEPRECATION_WARNINGS  _Pragma("GCC diagnostic warning \"-Wdeprecated-declarations\"")
+#        define FF_DISABLE_DEPRECATION_WARNINGS _Pragma("GCC diagnostic push") _Pragma("GCC diagnostic ignored \"-Wdeprecated-declarations\"")
+#        define FF_ENABLE_DEPRECATION_WARNINGS  _Pragma("GCC diagnostic pop")
 #    endif
 #else
 #    define FF_DISABLE_DEPRECATION_WARNINGS