CWG1814 Default arguments in lambda-expressions
CWG1816 Unclear specification of bit-field values
CWG1817 Linkage specifications and nested scopes
CWG1824 Completeness of return type vs point of instantiation
CWG1830 Repeated specifiers
CWG1832 Casting to incomplete enumeration
CWG1834 Constant initialization binding a reference to an xvalue
CWG1843 Bit-field in conditional operator with throw operand
CWG1850 Differences between definition context and point of instantiation
CWG1851 decltype(auto) in new-expressions
CWG1852 Wording issues regarding decltype(auto)
N3918 Temporary objects vs temporary expressions

Also fixes CWG943, CWG1076, CWG1299, CWG1300, and CWG1651.

Split [expr.type.conv] (rewritten by this change) into bullets to
emphasize that we have three independent possibilities.