[Analyzer] Always use non-reference types when creating expressions in BodyFarm.

Remove an option to use a reference type (on by default!) since a
non-reference type is always needed for creating expressions, functions
with multiple boolean parameters are very hard to use, and in general it
was just a booby trap for further crashes.
Furthermore, generalize call_once test case to fix some of the crashes mentioned
https://bugs.llvm.org/show_bug.cgi?id=34869
Also removes std::call_once crash.

Differential Revision: https://reviews.llvm.org/D39015

llvm-svn: 316041