bookmaker error handling

Bookmaker will generate instructions on how to
fix detected errors in a few cases:
- if class function is missing description
- if global function is missing description
- if function parameters don't match doxygen
- if function parameters don't match bmh

(The last case above won't happen if bmh #Method
uses #Populate to retrieve parameter descriptions
from the include.)

Adding this revealed that globals weren't always
accounted for in bookmaker's cross-check; fix
that as well.

TBR=reed@google.com
Docs-Preview: https://skia.org/?cl=171224
Bug: skia:
Change-Id: Ic1b41d4722954fa8a42685a8fe7266b8a860c362
Reviewed-on: https://skia-review.googlesource.com/c/171224
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
10 files changed