Markdown filter: reinstate the inline code finder

*Created by: Kuro Kurosaka *

In commit 44b31f77 on 1/21/2018 (M36-SNAPSHOT), the inline code finder was disabled in order to use the HTML subfilter to parse the HTML in-line elements and HTML bloks in Markdown documents. This was done with understanding that the inline code finder and subfilter cannot coexist.

Since then I have learned that the inline code finder was used more widely than anticipated and received a request to reinstate it. In a more careful analysis, no apparent reason was found that the code finder and the HTTP subfilter would interfere each other in our particular usage where each section of the input document is either processed by the subfilter or the code finder but not both. In our experiment, they seem to work fine.

We should reinstate the inline code finder.