Add compiler flags which aren't included in -Wall or -Wextra

Adds the following compiler flags:
 . -Wduplicated-cond
 . -Wlogical-op
 . -Wformat-truncation
 . -fno-common

Author: Girgias

Zend/Zend.m4

@@ -215,6 +215,10 @@ fi
 test -n "$GCC" && CFLAGS="-Wall -Wextra -Wno-strict-aliasing -Wno-implicit-fallthrough -Wno-unused-parameter -Wno-sign-compare $CFLAGS"
 dnl Check if compiler supports -Wno-clobbered (only GCC)
 AX_CHECK_COMPILE_FLAG([-Wno-clobbered], CFLAGS="-Wno-clobbered $CFLAGS", , [-Werror])
+AX_CHECK_COMPILE_FLAG([-Wduplicated-cond], CFLAGS="-Wduplicated-cond $CFLAGS", , [-Werror])
+AX_CHECK_COMPILE_FLAG([-Wlogical-op], CFLAGS="-Wlogical-op $CFLAGS", , [-Werror])
+AX_CHECK_COMPILE_FLAG([-Wformat-truncation], CFLAGS="-Wformat-truncation $CFLAGS", , [-Werror])
+AX_CHECK_COMPILE_FLAG([-fno-common], CFLAGS="-fno-common $CFLAGS", , [-Werror])
 
 test -n "$DEBUG_CFLAGS" && CFLAGS="$CFLAGS $DEBUG_CFLAGS"