Revert "Merge pull request #301 from alan-baker/hpp1" (#302)

Revert "Merge pull request #301 from alan-baker/hpp1" (#302)

This reverts commit 747031e10dea9e6c5651bf11957a9dbcd379fa47, reversing
changes made to 85a1ed200d50660786c1a88d9166e871123cce39.

In other words, don't add the .hpp11 files to the BUILD.gn
That's because GN doesn't recognize .hpp11 extension as a C/C++
header file.

See https://bugs.chromium.org/p/gn/issues/detail?id=311

Instead, client dependencies should #include the .hpp11 file directly
even though that seems to hide it away from GN's visibility.
That seems wrong, but it does work.