Add "/" to the characters that can make up a "horizontal rule" comment that is converted to standard form.
Add "/" to the characters that can make up a "horizontal rule" comment
that is converted to standard form.

Allow continued comments (i.e., // followed by any characters that
terminate at line end with a backslash) just for the case where the
next line is also marked as a comment line (marked by zero or more
blanks followed by // at the start of the line) as well.

Substantially tighten logic to deal with some corner cases.


svn path=/trunk/; revision=11294

FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot