Autoconf, CMake: Add a warning flag (-Wcomma)

Use of comma as statement separator is discouraged and reported as
warning by clang with -Wcomma.

Author: fxlb

CMakeLists.txt

@@ -1201,6 +1201,7 @@ if(EXISTS ${CMAKE_SOURCE_DIR}/.devel OR EXISTS ${CMAKE_BINARY_DIR}/.devel)
         check_and_add_compiler_option(-Wall)
         check_and_add_compiler_option(-Wassign-enum)
         check_and_add_compiler_option(-Wcast-qual)
+        check_and_add_compiler_option(-Wcomma)
         check_and_add_compiler_option(-Wmissing-prototypes)
         check_and_add_compiler_option(-Wmissing-variable-declarations)
         check_and_add_compiler_option(-Wold-style-definition)

aclocal.m4

@@ -807,6 +807,7 @@ AC_DEFUN(AC_LBL_DEVEL,
 		    AC_LBL_CHECK_COMPILER_OPT($1, -Wall)
 		    AC_LBL_CHECK_COMPILER_OPT($1, -Wassign-enum)
 		    AC_LBL_CHECK_COMPILER_OPT($1, -Wcast-qual)
+		    AC_LBL_CHECK_COMPILER_OPT($1, -Wcomma)
 		    AC_LBL_CHECK_COMPILER_OPT($1, -Wmissing-prototypes)
 		    AC_LBL_CHECK_COMPILER_OPT($1, -Wmissing-variable-declarations)
 		    AC_LBL_CHECK_COMPILER_OPT($1, -Wnull-pointer-subtraction)