This will make sure that all file descriptors are closed through the use of the start() function.
. if $MACHINE_ARCH is unknown, use $MACHINE like in libc . fixes test51 compilation for gcc/clang (with other compile and link fixes)
swapcontext, and makecontext). - Fix VM to not erroneously think the stack segment and data segment have collided when a user-space thread invokes brk(). - Add test51 to test ucontext functionality. - Add man pages for ucontext system calls.
