analyzer: fix ICE on __builtin_ms_va_copy [PR105765]

analyzer: fix ICE on __builtin_ms_va_copy [PR105765]

gcc/analyzer/ChangeLog:
	PR analyzer/105765
	* varargs.cc (get_BT_VALIST_ARG): Rename to...
	(get_va_copy_arg): ...this, and update logic for determining level
	of indirection of va_copy's argument to use type of argument,
	rather than looking at va_list_type_node, to correctly handle
	__builtin_ms_va_copy.
	(get_stateful_BT_VALIST_ARG): Rename to...
	(get_stateful_va_copy_arg): ...this.
	(va_list_state_machine::on_va_copy): Update for renaming.
	(region_model::impl_call_va_copy): Likewise.

gcc/testsuite/ChangeLog:
	PR analyzer/105765
	* gcc.dg/analyzer/stdarg-1-ms_abi.c: New test, based on stdarg-1.c.
	* gcc.dg/analyzer/stdarg-1-sysv_abi.c: Likewise.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>