Ignore trailing NullStmts in StmtExprs for GCC compatibility.

Ignore trailing NullStmts in StmtExprs for GCC compatibility.

Ignore trailing NullStmts in compound expressions when determining the result type and value. This is to match the GCC behavior which ignores semicolons at the end of compound expressions.

Patch by Dominic Ferreira.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@365498 91177308-0d34-0410-b5e6-96231b3b80d8