cpp11-migrate: Refactor how global options are passed to Transforms

Refactored how global options are passed to Transforms to avoid widespread
changes every time a new global option is added.

Tests updated to reflect new interface.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@183443 91177308-0d34-0410-b5e6-96231b3b80d8
cpp11-migrate: Add EnableHeaderModification flag

First step toward supporting header modifications: adding a flag that turns on
such modifications. Eventually header modifications will be on by default but
until all the kinks can be worked out, they must be explicitly enabled.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@183444 91177308-0d34-0410-b5e6-96231b3b80d8