Fix lookup of initialized captures in unevaluated context.
* cp-tree.h (DECL_NORMAL_CAPTURE_P): New.
* name-lookup.c (qualify_lookup): Check it.
* parser.c (cp_parser_lambda_introducer): Pass explicit_init_p
to add_capture.
* semantics.c (add_capture): Set DECL_NORMAL_CAPTURE_P
on captures without explicit init.
(add_default_capture): Pass explicit_init_p.
Fix capture by copy of types with explicit copy constructor.
* cp-tree.h (TARGET_EXPR_DIRECT_INIT_P): New.
(DIRECT_INIT_EXPR_P): New.
* typeck.c (convert_for_initialization): Just return if
DIRECT_INIT_EXPR_P.
* parser.c (cp_parser_lambda_introducer): Use
TARGET_EXPR_DIRECT_INIT_P for normal captures.