• Build.sh: fix NSIG detection for gcc-snapshot

• all: bump version to R50-current; add more comments; whitespace
• all: remove all mkssert(); we’ll do full re-runs of scan-build and,
  hopefully, Coverity Scan/Prevent
• check.t: fix a testcase (sed could exit false, but we don’t care)
• eval.c: fix tilde_ok data type (only unsigned may shl constantly)
• exec.c: fix shebang buf array accesses to always go via uint8_t *

main.c

@@ -34,7 +34,7 @@
 #include <locale.h>
 #endif
 
-__RCSID("$MirOS: src/bin/mksh/main.c,v 1.285 2014/10/12 21:58:52 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/main.c,v 1.286 2014/11/25 21:13:28 tg Exp $");
 
 extern char **environ;
 
@@ -1014,8 +1014,6 @@ cleanup_parents_env(void)
 	struct env *ep;
 	int fd;
 
-	mkssert(e != NULL);
-
 	/*
 	 * Don't clean up temporary files - parent will probably need them.
 	 * Also, can't easily reclaim memory since variables, etc. could be