print warnings if

gcc ignores inline directives
pointer arithmetic with void pointers
...

Originally committed as revision 6134 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -1469,6 +1469,10 @@ enabled debug && add_cflags -g
 check_cflags -Wdeclaration-after-statement
 check_cflags -Wall
 check_cflags -Wno-switch
+check_cflags -Wdisabled-optimization
+check_cflags -Wpointer-arith
+check_cflags -Wredundant-decls
+check_cflags -Winline
 
 # add some linker flags
 check_ldflags '-Wl,--as-needed' '-Wl,-rpath-link,\$(BUILD_ROOT)/libavcodec' '-Wl,-rpath-link,\$(BUILD_ROOT)/libavformat' '-Wl,-rpath-link,\$(BUILD_ROOT)/libavutil'