[Parser] Perform CachedTokens update dependent on token consumption

In the context where we break one tok::greatergreater into two
tok::greater in order to correctly update the cached tokens; update the
CachedTokens with two tok::greater only if ParseGreaterThanInTemplateList
clients asks to consume the last token. Otherwise we only need to add
one because the second is already added later on, as a not yet cached token.

Differential Revision: http://reviews.llvm.org/D16906

rdar://problem/24488367

llvm-svn: 259910