Fix ICEs related to VM types in C 1/2 [PR70418, PR107557, PR108423]

Fix ICEs related to VM types in C 1/2 [PR70418, PR107557, PR108423]

Size expressions were sometimes lost and not gimplified correctly, leading to
ICEs and incorrect evaluation order.  Fix this by 1) not recursing into
pointers when gimplifying parameters in the middle-end (the code is merged with
gimplify_type_sizes), which is incorrect because it might access variables
declared later for incomplete structs, and 2) tracking size expressions for
struct/union members correctly, 3) emitting code to evaluate size expressions
for missing cases (nested functions, empty declarations, and structs/unions).

	PR c/70418
	PR c/106465
	PR c/107557
	PR c/108423

	gcc/c/
	* c-decl.cc (start_decl): Make sure size expression are
	evaluated only in correct context.
	(grokdeclarator): Size expression in fields may need a bind
	expression, make sure DECL_EXPR is always created.
	(grokfield, declspecs_add_type): Pass along size expressions.
	(finish_struct): Remove unneeded DECL_EXPR.
	(start_function): Evaluate size expressions for nested functions.
	* c-parser.cc (c_parser_struct_declarations,
	c_parser_struct_or_union_specifier): Pass along size expressions.
	(c_parser_declaration_or_fndef): Evaluate size expression.
	(c_parser_objc_at_property_declaration,
	c_parser_objc_class_instance_variables): Adapt.
	* c-tree.h (grokfield): Adapt declaration.

	gcc/testsuite/
	* gcc.dg/nested-vla-1.c: New test.
	* gcc.dg/nested-vla-2.c: New test.
	* gcc.dg/nested-vla-3.c: New test.
	* gcc.dg/pr70418.c: New test.
	* gcc.dg/pr106465.c: New test.
	* gcc.dg/pr107557-1.c: New test.
	* gcc.dg/pr107557-2.c: New test.
	* gcc.dg/pr108423-1.c: New test.
	* gcc.dg/pr108423-2.c: New test.
	* gcc.dg/pr108423-3.c: New test.
	* gcc.dg/pr108423-4.c: New test.
	* gcc.dg/pr108423-5.c: New test.
	* gcc.dg/pr108423-6.c: New test.
	* gcc.dg/typename-vla-2.c: New test.
	* gcc.dg/typename-vla-3.c: New test.
	* gcc.dg/typename-vla-4.c: New test.
	* gcc.misc-tests/gcov-pr85350.c: Adapt.