Fix PR objc/68438 (uninitialized source ranges)

Fix PR objc/68438 (uninitialized source ranges)

gcc/c/ChangeLog:
	PR objc/68438
	* c-parser.c (c_parser_postfix_expression): Set up source ranges
	for various Objective-C constructs: Class.name syntax,
	@selector(), @protocol(), @encode(), and [] message syntax.

gcc/testsuite/ChangeLog:
	PR objc/68438
	* objc.dg/plugin: New subdirectory.
	* objc.dg/plugin/diagnostic-test-expressions-1.m: New test file.
	* objc.dg/plugin/plugin.exp: New file, based on
	gcc.dg/plugin/plugin.exp.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@230775 138bc75d-0d04-0410-961f-82ee72b054a4