Building with developer flags should always use -Werror

The extension requires PHP 5.4+, so the PHP version check was redundant.

Author: jmikola

config.m4

@@ -129,10 +129,7 @@ if test "$MONGODB" != "no"; then
     PHP_CHECK_GCC_ARG(-Wempty-body,                     _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Wempty-body")
     PHP_CHECK_GCC_ARG(-Wparentheses,                    _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Wparentheses")
     PHP_CHECK_GCC_ARG(-Wdeclaration-after-statement,    _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Wdeclaration-after-statement")
-
-    if test "$PHP_FOUND_VERNUM" -ge "50400"; then
-      PHP_CHECK_GCC_ARG(-Werror,                        _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Werror")
-    fi
+    PHP_CHECK_GCC_ARG(-Werror,                          _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Werror")
 
     MAINTAINER_CFLAGS="-Wextra $_MAINTAINER_CFLAGS  -Wno-unused-parameter -Wno-unused-but-set-variable -Wno-missing-field-initializers"
     STD_CFLAGS="-g -O0 -Wall"