Rename directory housing clang-include-fixer to be eponymous

Makes the name of this directory consistent with the names of the other
directories in clang-tools-extra.

Similar to r356254. No intended behavior change.

Differential Revision: https://reviews.llvm.org/D59750

llvm-svn: 356897
GitOrigin-RevId: 43356f56bd2ede05c70db537e3f8b50a31444487
73 files changed