Fix a crash in the static analyzer (bug #16307)

Summary:
When processing a call to a function, which got passed less arguments than it
expects, the analyzer would crash.

I've also added a test for that and a analyzer warning which detects these
cases.

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D994

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@184288 91177308-0d34-0410-b5e6-96231b3b80d8