Richard Smith b9b05100c5 Factor out repeated code parsing and concatenating header-names from
tokens.

We now actually form an angled_string_literal token for a header name by
concatenation rather than just working out what its contents would be.
This substantially simplifies downstream processing and is necessary for
C++20 header unit imports.

llvm-svn: 356433
2019-03-19 01:51:19 +00:00
..
2018-07-17 04:56:22 +00:00