Allow splitting between string literals and identifiers.

Also don't break in long include directives as that is not desired.

We can now format:

  #include "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
  #define LL_FORMAT "ll"
  printf("aaaaa: %d, bbbbbbbbb: %" LL_FORMAT "d, cccccccc: %" LL_FORMAT
         "d, ddddddddd: %" LL_FORMAT "d\n");

Before, this led to weird results.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@175959 91177308-0d34-0410-b5e6-96231b3b80d8