Fixes markdown formatting errors and some functions not showing
up in the generated documentation at all.
Ruby script (gendoc.rb) fixes:
* Modified automatic instertion of backquotes:
* Don't add backquotes around names which are already preceded by a
backquote. Fixes for example \`RedisModule_Reply\*\` which turning
into \`\`RedisModule_Reply\`\*\` messes up the formatting.
* Add backquotes around types such as RedisModuleString (in addition
to function names `RedisModule_[A-z()]*` and macro names
`REDISMODULE_[A-z]*`).
* Require 4 spaces indentation for disabling automatic backquotes, i.e.
code blocks. Fixes continuations of list items (indented 2 spaces).
* More permissive extraction of doc comments:
* Allow doc comments starting with `/**`.
* Make space before `*` on each line optional.
* Make space after `/*` and `/**` optional (needed when appearing on
its own line).
Markdown fixes in module.c:
* Fix code blocks not indented enough (4 spaces needed).
* Add black line before code blocks and lists where missing (needed).
* Enclose special markdown characters `_*^<>` in backticks to prevent them
from messing up formatting.
* Lists with `1)` changed to `1.` for proper markdown lists.
* Remove excessive indentation which causes text to be unintentionally
rendered as code blocks.
* Other minor formatting fixes.
Other fixes in module.c:
* Remove blank lines between doc comment and function definition. A blank
line here makes the Ruby script exclude the function in docs.
