A bunch of compat work (mostly stubs but some real implementations, too.)

Another pass at getting bash-1.14.7 to build. Not that many symbols remain.

LibC/setjmp.cpp

@@ -0,0 +1,13 @@
+#include <setjmp.h>
+#include <assert.h>
+#include <Kernel/Syscall.h>
+
+int setjmp(jmp_buf)
+{
+    assert(false);
+}
+
+void longjmp(jmp_buf, int val)
+{
+    assert(false);
+}