options.texi (EnabledBy): Document that the argument must be a Common option.

options.texi (EnabledBy): Document that the argument must be a Common option.

gcc/ChangeLog:

2015-08-09  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	* doc/options.texi (EnabledBy): Document that the argument must be
	a Common option.
	* doc/invoke.texi (Wnull-dereference): Move after Wnonnull.
	Not enabled by -Wall.
	* optc-gen.awk: Give nicer error messages. Detect if the argument
	of EnabledBy is not a Common option.
	* common.opt (Wnull-dereference): Not enabled by -Wall.
	* opt-functions.awk (lang_enabled_by): Nicer error messages.

gcc/c-family/ChangeLog:

2015-08-09  Manuel López-Ibáñez  <manu@gcc.gnu.org>

	* c.opt (Wchkp): Use LangEnabledBy instead of EnabledBy.

From-SVN: r226751