Add all developer build flags in a consistent manner

Author: jmikola

config.m4

@@ -130,8 +130,12 @@ if test "$MONGODB" != "no"; then
     PHP_CHECK_GCC_ARG(-Wparentheses,                    _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Wparentheses")
     PHP_CHECK_GCC_ARG(-Wdeclaration-after-statement,    _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Wdeclaration-after-statement")
     PHP_CHECK_GCC_ARG(-Werror,                          _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Werror")
+    PHP_CHECK_GCC_ARG(-Wextra,                          _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Wextra")
+    PHP_CHECK_GCC_ARG(-Wno-unused-parameter,            _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Wno-unused-parameter")
+    PHP_CHECK_GCC_ARG(-Wno-unused-but-set-variable,     _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Wno-unused-but-set-variable")
+    PHP_CHECK_GCC_ARG(-Wno-missing-field-initializers,  _MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS -Wno-missing-field-initializers")
 
-    MAINTAINER_CFLAGS="-Wextra $_MAINTAINER_CFLAGS  -Wno-unused-parameter -Wno-unused-but-set-variable -Wno-missing-field-initializers"
+    MAINTAINER_CFLAGS="$_MAINTAINER_CFLAGS"
     STD_CFLAGS="-g -O0 -Wall"
   fi