Modified 'jam0' in the Makefile to './jam0'
Fixed a bug in my 'dynamic command size' extension. It wasn't dealing
with piecemeal targets properly
In execcmd(), reverted to 2.2 behaviour for the logic on NT of when
to write a command to a .bat file, and when to invoke the shell
directly. The cmd.exe interpreter has limitations on how large the
lines in it can be. We were invoking rc.exe with a long command line,
and it was failing when invoked via a .bat file