[analyzer] -drain is not an alias for -release.

This was previously added to support -[NSAutoreleasePool drain], which
behaves like -release under non-GC and "please collect" under GC. We're
not currently modeling the autorelease pool stack, though, so we can
just take this out entirely.

Fixes PR14927.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172444 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] Fix cast-away-const warning by using const_cast.

Patch by David Greene, modified by me.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172445 91177308-0d34-0410-b5e6-96231b3b80d8
[analyzer] Add ProgramStatePartialTrait<const void *>.

This should fix cast-away-const warnings reported by David Greene.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172446 91177308-0d34-0410-b5e6-96231b3b80d8