[analyzer] Re-enable constructors when lifetime extension through fields occurs.

Temporary object constructor inlining was disabled in r326240 for code like

    const int &x = A().x;

because automatic destructor for the lifetime-extended object A() was not
working correctly in CFG.

CFG was fixed in r333941, so inlining can be re-enabled. CFG for lifetime
extension through aggregates still needs to be fixed.

Differential Revision: https://reviews.llvm.org/D44239

llvm-svn: 333946