Add exec and pipe functions.

* configure: Check for pipe.

* sysif.c (exec_wrap, pipe_wrap): New static functions.
(sysif_init): Register exec and pipe intrinsics.

* txr.1: Documented exec and pipe.

* tl.vim, txr.vim: Regenerated.

1 files changed, 19 insertions, 0 deletions

diff --git a/configure b/configure
index 992f014b..ef86a423 100755
--- a/configure
+++ b/configure
@@ -1889,6 +1889,25 @@ else
   printf "no\n"
 fi
 
+printf "Checking for pipe ... "
+cat > conftest.c <<!
+#include <unistd.h>
+
+int main(void)
+{
+  int p[2];
+  int r = pipe(p);
+  return 0;
+}
+!
+if conftest ; then
+  printf "yes\n"
+  printf "#define HAVE_PIPE 1\n" >> $config_h
+else
+  printf "no\n"
+fi
+
+
 printf "Checking for _wspawnlp ... "
 
 cat > conftest.c <<!