sh: Don't modify exit status when break/continue/return passes !.

This matches what would happen if  ! P  were to be replaced with
if P; then false; else true; fi.

Example:
  f() { ! return 0; }; f

1 files changed, 2 insertions, 0 deletions

diff --git a/bin/sh/eval.c b/bin/sh/eval.c
index 0972b10..d3708b3 100644
--- a/bin/sh/eval.c
+++ b/bin/sh/eval.c
@@ -279,6 +279,8 @@ evaltree(union node *n, int flags)
 			break;
 		case NNOT:
 			evaltree(n->nnot.com, EV_TESTED);
+			if (evalskip)
+				goto out;
 			exitstatus = !exitstatus;
 			break;