[analyzer] Teach CallEvent about C++17 aligned operator new().

In C++17, when class C has large alignment value, a special case of
overload resolution rule kicks in for expression new C that causes the aligned
version of operator new() to be called. The aligned new has two arguments:
size and alignment. However, the new-expression has only one "argument":
the construct-expression for C(). This causes a false positive in
core.CallAndMessage's check for matching number of arguments and number
of parameters.

Update CXXAllocatorCall, which is a CallEvent sub-class for operator new calls
within new-expressions, so that the number of arguments always matched
the number of parameters.

rdar://problem/44738501

Differential Revision: https://reviews.llvm.org/D52957

llvm-svn: 344539