Handle multiple consecutive __extension__ tokens
__builtin_va_list can be KEYWORD'd
Removed parse_curtok_is_type() in favour of parse_at_decl()
Type header cleanup
Parse and ICE() on __auto_type
Handle __auto_type parse errors more gracefully
__auto_type placeholder and initialiser type inference
__auto_type tests
Pulled out warn/die_at() to warn.[ch]
__attribute__((__ucc_debug)) for debugging attribute use
Tests for __auto_type qualifier and attribute preservation
Merge branch 'feature/__auto_type'