ash: don't rely on libc signal names

The bsd signal names are out-of-order compared to the minix ones.

I found out (the hard way) that the (MINIX-descending) ordered list of
signals in <sys/signal.h> does not match the (BSD-descending) ordered
list of signals in usr/src/lib/libc/nbsd_libc/gen/sig{name,list}.c

Beyond being unfortunate, it prevents the trap command of ash to handle
correctly a named signal; a funny test case is
        #!/bin/sh
        trap 'echo trapping signal BUS' BUS
        trap 'echo trapping signal 10 (USR1)' 10
        trap # show me what is currently trapped

As a quick workaround, I disabled the use of the libc-provided
sys_sig{name,list} arrays for ash, and reverted to the hand-made array
which is used by the less capable MINIX libc. It allowed me to use
pkgsrc.

commands/ash/trap.c

@@ -62,8 +62,10 @@ __FBSDID("$FreeBSD: src/bin/sh/trap.c,v 1.29 2004/04/06 20:06:51 markm Exp $");
 #endif
 #include "builtins.h"
 
-#if defined(__minix) && !defined(__NBSD_LIBC)
+#if defined(__minix)
+#if !defined(__NBSD_LIBC)
 #define NO_SIGINTERRUPT
+#endif
 #define NO_SYS_SIGNAME
 #define NO_SYS_SIGLIST
 #endif