Fix a loop overrun in ComputePreamble when the last remapped file was erased,
and reenable crash recovery test.
 - Reparsing is still very crashy / weird, so I had to sprinkle random code into
   the remapped input to get it to do what I want (i.e., crash!).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@111550 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed