new functions: find-symbol and find-symbol-fb.

Turns out, there is already a find_symbol in lib.c, completely
unused.

* eval.c (eval_init): Register find-symbol and find-symbol-fb
intrinsics.

* lib.c (find_symbol): Fix this hitherto unused function to do
correct defaulting of the package argument and, to accept an
additional argument specifying the not-found value.
(find_symbol_fb): New function.

* lib.c (find_symbol): Declaration updated.
(find_symbol_fb): Declared.

* txr.1: Documented.

1 files changed, 2 insertions, 1 deletions

diff --git a/lib.h b/lib.h
index c7296b7b..c22e9890 100644
--- a/lib.h
+++ b/lib.h
@@ -891,7 +891,8 @@ val use_package(val use_list, val package);
 val unuse_package(val unuse_list, val package);
 val symbol_visible(val package, val sym);
 val symbol_needs_prefix(val self, val package, val sym);
-val find_symbol(val str, val package);
+val find_symbol(val name, val package, val notfound_val);
+val find_symbol_fb(val name, val package, val notfound_val);
 val intern(val str, val package);
 val unintern(val sym, val package);
 val rehome_sym(val sym, val package);