[Bug c++/126843] New: The module mapper format does not support header paths with spaces or tabs in them

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126843

            Bug ID: 126843
           Summary: The module mapper format does not support header paths
                    with spaces or tabs in them
           Product: gcc
           Version: 12.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bugzilla.gcc at me dot benboeckel.net
  Target Milestone: ---

Or newlines, but that's a smaller issue.

I think supporting quotes should be fine. "No one" is using headers with spaces
today, and quotes are not otherwise allowed (unless someone really has a header
ending in a double quote), so I think supporting `"` with `\` escaping for
double quotes, tabs, newlines, and `\` itself seems fine to me (erroring for
unknown escape sequences).

Note that CMake today will write header units as `"quoted.hpp"` and
`<brackets.h>` but header units are not actually supported, so I'm fine with
supporting the new format without worrying about older GCC support at least.

Noticed by https://github.com/talisein at
https://github.com/mesonbuild/meson/issues/5024#issuecomment-5275003293