expr.h indentation
Virtualised expression-lvalue decisions
_Generic propagates lvalue-ness
Factored out __builtin_choose_expr's sub-expression logic
__builtin_choose_expr() propagates lvalue-ness
Moved struct-copy-init bug to ignores
Merge branch 'master' into experimental/float

Conflicts:
	src/cc1/expr.h
	src/cc1/ops/__builtin.c
_Generic test fix