[CodeComplete] Propagate preferred types through parser in more cases

Preferred types are used by code completion for ranking. This commit
considerably increases the number of points in code where those types
are propagated.

In order to avoid complicating signatures of Parser's methods, a
preferred type is kept as a member variable in the parser and updated
during parsing.

Differential revision: https://reviews.llvm.org/D56723

llvm-svn: 352788