[demangler] Fix a crash in the demangler during parsing of a lamdba

The problem is that multiple types could have been parsed from parse_type(),
which the lamdba parameter parsing didn't handle.

Differential revision: https://reviews.llvm.org/D33368

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@303718 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed