Author: Kev <klmitch@mit.edu>

Log message:

Don't allow G-lines to have 0 lastmod--return a "need more params" message
if lastmod evaluates to 0.  This solves the bug where not passing a lastmod
resulted in an assertion failure in gline_propagate().

git-svn-id: file:///home/klmitch/undernet-ircu/undernet-ircu-svn/ircu2/branches/u2_10_12_branch@1799 c9e4aea6-c8fd-4c43-8297-357d70d61c8c