[analyzer] Detect duplicate [super dealloc] calls

Add an alpha path checker that warns about duplicate calls to [super dealloc].
This will form the foundation of a checker that will detect uses of
'self' after calling [super dealloc].

Part of rdar://problem/6953275.

Based on a patch by David Kilzer!

Differential Revision: http://reviews.llvm.org/D5238

llvm-svn: 261545