Fix va_arg type location

Fix va_arg type location

Now that diagnostics first point to the spelling location of tokens
coming from macro expansion, the test case
gcc/testsuite/g++.old-deja/g++.other/vaarg3.C shows that when I write
va_args (args, some_type), the location that is recorded for
"some_type" is not correct.  We wrongly record a location that is in
the system header where the va_args macro is defined.

This patch changes that to correctly record the location for the type
operand of the va_arg expression.

With this patch applied, the
gcc/testsuite/g++.old-deja/g++.other/vaarg3.C test PASSes with and
without -ftrack-macro-expansion.

Tested on x86_64-unknown-linux-gnu against trunk.

Note that the bootstrap with -ftrack-macro-expansion exhibits other
separate issues that are addressed in subsequent patches.  This patch
just fixes one class of problems.

The patch does pass bootstrap with -ftrack-macro-expansion turned off,
though.

gcc/cp/

	* cp-tree.h (build_x_va_arg): Take an additional location
	parameter.
	* call.c (build_x_va_arg): Take a loc parameter for the location
	of the type of the va_arg expression.
	* parser.c (cp_parser_primary_expression): Pass the type of the
	type in the va_arg expression to build_x_va_arg.
	* pt.c (tsubst_copy): Adjust calls to build_x_va_arg.

From-SVN: r186973