No more shlib, only a single exe.

This is a proposal for simplifying a bit the code base. Basically, I got rid of all source files but tclAppInit.c. I no longer build a shared library, and require the Tcllauncher package directly from Tcl_AppInit. Also, pkgIndex.tcl only sources the tcllauncher-support.tcl file. I integrated the threads branch. See if you're interested in these changes..