Avoid indent-pre when line contains block tags

 * Accumulate the current line in PreHandler to back out of indent-pre
   wrapping when blocks are encountered.

 * Look ahead when serializing sol - pre for blocks on the line to avoid
   nowiki escaping, while being mindful of newline inducing blocks.

 * Failing test is the result of a trailing newline which will hopefully
   get cleaned up in one of Subbu's patches.

Change-Id: I130bcad0437d2b1aaa7a38d3cfbcd54cda33756d