Remove trivial destructor from SVal.

This enables the faster SmallVector in clang and also allows clang's unused
variable warnings to be more effective. Fix the two instances that popped up.

The RetainCountChecker change actually changes functionality, it would be nice
if someone from the StaticAnalyzer folks could look at it.

git-svn-id: 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed