[analyzer] Re-enable C++17-specific variable and member construction contexts.

Not contexts themselves, but rather support for them in the analyzer.

Such construction contexts appear when C++17 mandatory copy elision occurs
during initialization, and presence of a destructor causes a
CXXBindTemporaryExpr to appear in the AST.

Similar C++17-specific constructors for return values are still to be supported.

Differential Revision: https://reviews.llvm.org/D47351

llvm-svn: 334683