Chaitanya Koparkar authored May 03, 2018 and Ben Gamari committed May 03, 2018

GHC and the build tools use "response files" to work around the limit
on the length of command line arguments on Windows. Haddock's
implementation of parsing response files (i.e escaping/unescaping the
appropriate characters) seems complete, is well tested, and also
closely matches the GCC version. This patch moves the relevant bits
into `base` so that it's easier for other libraries to reuse it.

Test Plan: make test TEST=T13896

Reviewers: bgamari, RyanGlScott, 23Skidoo, hvr

Reviewed By: RyanGlScott

Subscribers: thomie, carter

GHC Trac Issues: #13896

Differential Revision: https://phabricator.haskell.org/D4612