The biggest changes were related to 10.0's replacing gcc with clang
and the switch to a new package system. The former required various
fixes to Makefiles that hardwired "gcc" and also missing prototypes
in source files that clang is particularly obnoxious about.

There was also accomodating the normal evolution of the ports tree.
New variables were needed in many of the Makefiles for this. Hopefully,
all the changes I made are backward compatible, but I don't actually
care that much since I hope to never, ever have to remake those older
packages! A new emulab version of the m2crypto port was needed to
reflect that m2crypto is no longer installed as an .egg file.

Casualties:

  * Emulab assign. As of this commit, assign does not build with
    clang. It will build, but immediately core dumps if built with
    a gcc port (gcc46 below). THIS NEEDS TO BE FIXED!

  * Emulab nsverify. This requires building a pure ns-2.34, which
    is old and does not compile with clang. Yo...