Fixed bitfield tests (don't rely on printf())
caret_check takes cc args
Test fixes
Look through typedefs for nested structs/unions/enums

This fixes the Plan 9 nested-struct extension nested, e.g.
typedef struct A { int i; } A;
struct B
{
	A;
};

B *b = ...;
b->i;

However the problem is the separation of the parse and fold stages -
these need merging so we have the correct typedef (and other)
information about variables when parsing structures using them.
layout_check accepts $CFLAGS (fixes Plan 9 extenion test)
retcheck takes $CFLAGS - fixes another Plan 9 extension test
Fixed nested struct-inside-struct acting as a new decl
Drop ignored decls from a struct to avoid init
Anonymous structs/Plan 9 extension test fixes
cpp2: split out undef warnings - #undef and #if abc
Fresh test run