Support customizing doctypes, fixes #15
Support customizing doctypes, fixes #15

This patch implements MarkdownDoctype, which allows user to specify the doctype
to use for their content.  Most (if not all) previously  specification-specific
markup has been replaced by `switch` and `case`es to output correct ones accor-
ding to the selected doctype, also the responses' `Content-Type` are set accor-
ding to the doctype.

N.B.

* The bunch of switches and cases and enums probably ugly as hell and unprofes-
  sional
* Doctype definitions should be separated into a header files
* This patch introduces strings.h dependency from the C library for config str-
  ing comparing, probably there's a Apache equivalent/superseding function to
  use instead
* The coding style is mimicked but not carefully examined
* The Apache log calls are attempted but not carefully examined

Anyway please review.

Signed-off-by: 林博仁 <e1a755dad2798d70422023dceee1245c3d6b4517@gmail.com>

hamano/apache-mod-markdown