awk: widen scope of redirection macros.

This change makes it possible to use the redirection macros
like -> and ->> everywhere in the awk macro, including the
init-forms of the :let clause.

* stdlib/awk.tl (sys:awk-mac-let-outer): New macro.
(sys:awk-mac-let): Move redirection macros into
awk-mac-let-outer.
(awk): Rearrange the order of wrapping. We split the
let so the awk-retval and aws-sym are bound outermost.
Then we have the outer macros that provide the
redirection operators. Then the application-defined
lets inside of that.

* txr.1: Documented wide scope of redirection macros.

1 files changed, 8 insertions, 0 deletions

diff --git a/txr.1 b/txr.1
index b18b529f..f1d5d6ea 100644
--- a/txr.1
+++ b/txr.1
@@ -69716,6 +69716,14 @@ or
 string, direction and type, a new stream is not opened; rather, the
 previously associated stream is used.
 
+The scope of these macros is the entire containing
+.code awk
+form; they may be used in the
+.metn init-form s
+of the
+.code :let
+clause.
+
 The
 .code ->
 macro indicates that the file named