[CodeComplete] Add a bit more whitespace to completed patterns

Summary:
E.g. we now turn `while(<#cond#>){` into `while (<#cond#>) {`

This slightly improves the final output. Should not affect clients that
format the result on their own.

Reviewers: gribozavr

Reviewed By: gribozavr

Subscribers: jkorous, arphaman, kadircet, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D62616

llvm-svn: 362363