Allocate the signal stack on DOSEMU's stack instead of allocating it
statically. Now it is possible to link with Linuxthreads without
crashing, because the thread handling code is no longer confused
about the thread id of the stack it is using.


git-svn-id: https://dosemu.svn.sourceforge.net/svnroot/dosemu/trunk@606 7758b857-130e-0410-ab9c-d8735a528d18