Add No Wiki Escape Proposal

The nowiki and preformatted markup syntax doesn't let us quote actual markup for nowiki and preformatted themselves-- this is especially needed when talking about the syntax or explaining it. That's why there is a need to modify or extend the syntax, so that it is possible to include "}}}" in them.

The solution chosen for nowiki is to include any trailing "}" into the nowiki span, so that this:

{{{foo}}}}}}

will produce (for whatver actual markup is used instead of <nowiki>):

<nowiki>foo}}}</nowiki>

The preformatted markup syntax requires some kind of an escaping mechanism. Fortunately, the escaping is only necessary when there is "}}}" at the beginning of a line present in the block. In this case, to avoid treating the braces as markup for the end of the block, it needs to be indented with a single space. Furthermore, any line consisting of only indented three closing curly braces will have one space removed from the indentation -- to allow representing any possible text inside the preformatted block.

So, for example, this markup:

{{{
int main(int argc, char *argv[]) {
 if argc>0 {
   if argc<=1 {
     --argc;
 }}}
}}}

will produce this result:

<pre>
int main(int argc, char *argv[]) {
 if argc>0 {
   if argc<=1 {
     --argc;
}}}
</pre>