DOT is a graph description language, described at
<https://graphviz.org/doc/info/lang.html>. The new syntax file
recognizes the basic language keywords and syntax; known node,
edge, graph, etc. properties; comments; character strings.
The syntax file seems to work well with various DOT files found
in the Linux kernel sources as well as with the MNT Reform 2.0D-4
System Diagram.
Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
