Condense embedded formulas.

Bookmaker delimits formulas and equations to allow
representing variables and symbols without tripping
up reference lookup, spell checking, and comment
generation.

Before, formulas were represented with:
some text
#Formula
(x + y, 0)
##
, and more text

This made it difficult to know when spacing should
be preserved before and after the formula. Now,
formulas are represented with:
some text #Formula # (x + y, 0) ##, and more text

The presence or absence of a space between ## and ,
is now significant (before it was not).

Also, formulas are bracketed by <code> in markdown
generation, so that variables stand out better.
See:
https://skia.org/user/api/SkBlendMode_Reference?cl=152781#Dst_Out
for an example.

Also fixed 100 column offenders and added a code
check to identify them. For the moment, 100 column
offenders are outed with SkDebugf but their presence
does not cause bookmaker to fail.

TBR=caryclark@google.com

Docs-Preview: https://skia.org/?cl=152781
Bug: skia:6898
Change-Id: If92a65a234f5d616bf4485984a8d219a6f04821a
Reviewed-on: https://skia-review.googlesource.com/152781
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
32 files changed