configure: add regular compilation warnings for Objective C

configure.ac

@@ -1199,6 +1199,9 @@ AX_APPEND_COMPILE_FLAGS([-Wall -Wextra -Wsign-compare -Wundef -Wpointer-arith -W
 AC_LANG_PUSH(C++)
 AX_APPEND_COMPILE_FLAGS([-Wall -Wextra -Wsign-compare -Wundef -Wpointer-arith -Wvolatile-register-var -Wformat -Wformat-security -Wduplicated-branches -Wduplicated-cond], [CXXFLAGS])
 AC_LANG_POP(C++)
+AC_LANG_PUSH([Objective C])
+AX_APPEND_COMPILE_FLAGS([-Wall -Wextra -Wsign-compare -Wundef -Wpointer-arith -Wvolatile-register-var -Wformat -Wformat-security], [OBJCFLAGS])
+AC_LANG_POP([Objective C])
 
 dnl -Werror-implicit-function-declaration is used for the if_nametoindex detection with winstore
 AX_APPEND_COMPILE_FLAGS([-Wbad-function-cast -Wwrite-strings -Wmissing-prototypes -Werror-implicit-function-declaration -Winit-self -Wlogical-op -Wshadow=local -Wmultistatement-macros], [CFLAGS])
@@ -1214,7 +1217,7 @@ AS_IF([test "${enable_extra_checks}" = "yes"], [
     AX_APPEND_COMPILE_FLAGS([-Werror=missing-field-initializers -Werror=format -Werror=excess-initializers], [CXXFLAGS])
     AC_LANG_POP(C++)
     AC_LANG_PUSH([Objective C])
-    AX_APPEND_COMPILE_FLAGS([-Werror=missing-field-initializers -Werror=format -Werror=excess-initializers -Werror=incompatible-pointer-types -Werror=int-conversion -Werror=implicit-int], [OBJCFLAGS])
+    AX_APPEND_COMPILE_FLAGS([-Werror=missing-field-initializers -Werror=format -Werror=excess-initializers -Werror=incompatible-pointer-types -Werror=int-conversion -Werror=implicit-int -Wextra], [OBJCFLAGS])
     AC_LANG_POP([Objective C])
 ])