Fix location of sizeof/alignof (PR c++/80016)

Fix location of sizeof/alignof (PR c++/80016)

PR c++/80016 reports an issue with bizarre underlined range
for a complicated expression.

The root cause for the incorrect *starting* location of that range
is that alignof and sizeof expressions currently have
start == finish == caret at the opening parenthesis of the
expression.

This patch fixes this by generating appropriate start and finish
locations for alignof and sizeof expressions.

gcc/cp/ChangeLog:
	PR c++/80016
	* parser.c (cp_parser_unary_expression):  Generate a location
	range for alignof and sizeof expressions.

gcc/testsuite/ChangeLog:
	PR c++/80016
	* g++.dg/plugin/diagnostic-test-expressions-1.C (test_sizeof): New
	test function.
	(test_alignof): New test function.

From-SVN: r247108