• unify ksh_dup2() usage, use bool where appropriate

• apply diff from mirbsdksh-1.11:
  #ifdef DUP2_BROKEN
  /* Ultrix systems like to preserve the close-on-exec flag */
  ‣ XXX we do #ifdef __ultrix here (imake-style) instead of mirtoconfing it
    (but does anyone know of any other OS with the same problem? plus we’d
    see it as we now know the symptoms)
• remove ultrix Build.hs warn=' but might work…' in the hope it DOES

Build.sh

@@ -1,5 +1,5 @@
 #!/bin/sh
-srcversion='$MirOS: src/bin/mksh/Build.sh,v 1.311 2008/04/01 17:25:36 tg Exp $'
+srcversion='$MirOS: src/bin/mksh/Build.sh,v 1.312 2008/04/01 20:40:20 tg Exp $'
 #-
 # Environment used: CC CFLAGS CPPFLAGS LDFLAGS LIBS NOWARN NROFF TARGET_OS
 # CPPFLAGS recognised:	MKSH_SMALL MKSH_ASSUME_UTF8 MKSH_NOPWNAM MKSH_NOVI
@@ -342,8 +342,6 @@ syllable)
 ULTRIX)
 	: ${CC=cc -YPOSIX}
 	CPPFLAGS="$CPPFLAGS -Dssize_t=int"
-	warn=' but might work. I think that I/O'
-	warn="$warn${nl}redirs are kaput: child affects parent"
 	;;
 UWIN*)
 	ccpc='-Yc,'