[EH] Keep filter clauses for types that have been caught.

[EH] Keep filter clauses for types that have been caught.

The instruction combiner previously removed types from filter clauses in Landing Pad instructions if the type had previously been seen in a catch clause.  This is incorrect and prevents unexpected exception handlers from rethrowing the caught type.

Differential Revision: http://reviews.llvm.org/D14669

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253370 91177308-0d34-0410-b5e6-96231b3b80d8