chmod: work on streams and descriptors using fchmod.

* configure: extend chmod detection to cover fchmod.

* sysif.c (get_fd): New static functions.
(chmod_wrap): Include fchmod wrapping for integer
or stream argument.
(sysif_init): Register fchmod intrinsic.

1 files changed, 3 insertions, 2 deletions

diff --git a/configure b/configure
index d42e72bf..85336937 100755
--- a/configure
+++ b/configure
@@ -2278,13 +2278,14 @@ else
   printf "no\n"
 fi
 
-printf "Checking for chmod ... "
+printf "Checking for chmod/fchmod ... "
 cat > conftest.c <<!
 #include <sys/stat.h>
 
 int main(void)
 {
-  int r = chmod("a", S_IWUSR);
+  int r0 = chmod("a", S_IWUSR);
+  int r1 = fchmod(4, S_IWUSR);
   return 0;
 }
 !