Fixed a crash on replaying Preamble's PP conditional stack.

Summary:
The crash occurs when the first token after a preamble is a macro
expansion.
Fixed by moving replayPreambleConditionalStack from Parser into
Preprocessor. It is now called right after the predefines file is
processed.

Reviewers: erikjv, bkramer, klimek, yvvan

Reviewed By: bkramer

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D36872

llvm-svn: 311330