man pages update

man pages update

1) MSTP is fully supported by mstpd/mstpctl, it is not supported only by interface extension scripts (ifupdown). I have stated this point clearly;
2) Priority description reflects current status: priorities are in range 0-15. in natural units. When/if I'll be convinced that priorities should be in multiplies of 16/4096, we'll change the man pages accordingly. Perhaps, they'll be generated differently based on the conditional variable from the makefile. For now, they should describe things as they are;
3) Style, wording and other trivia.

Signed-off-by: Vitalii Demianets <dvitasgs@gmail.com>
Reviewed-by: Satish Ashok <sashok@cumulusnetworks.com>
git-svn-id: svn://svn.code.sf.net/p/mstpd/code/trunk@54 fbe50366-0c72-4402-a84b-5d246361dba7