[BuildTools] Revised trunk/coin.m4 with --enable-doscompile

[Lou Hafer]

Laci,

	If the configure/build script can observe COIN_SKIP_PROJECTS, that
makes it easy. Run_autotools and configure already look for it.

	Somewhere real soon, we'll be reinventing stuff that Bill Hart already
has for Acro.  Did anyone get the chance to listen to him talk at INFORMS, or
talk to him about his setup for testing and quality assurance? Is it something 
we can use outright, or easily adapt?

							Lou