changes for detecting and building for clang/binutils elf

and minor fixes:
 . add ack/clean target to lib, 'unify' clean target
 . add includes as library dependency
 . mk: exclude warning options clang doesn't have in non-gcc
 . set -e in lib/*.sh build files
 . clang compile error circumvention (disable NOASSERTS for release builds)

kernel/const.h

@@ -9,8 +9,10 @@
 #include "debug.h"
 
 /* Translate an endpoint number to a process number, return success. */
+#ifndef isokendpt
 #define isokendpt(e,p) isokendpt_d((e),(p),0)
 #define okendpt(e,p)   isokendpt_d((e),(p),1)
+#endif
 
 /* Constants used in virtual_copy(). Values must be 0 and 1, respectively. */
 #define _SRC_	0