Remove all \bcode / \ecode cruft; this is no longer needed.  See previous
checkin of myformat.sty.

Change "\renewcommand{\indexsubitem}{(...)}" to "\setindexsubitem{(...)}"
everywhere.

Some other minor nits that I happened to come across.
diff --git a/Doc/lib/libmpz.tex b/Doc/lib/libmpz.tex
index 7ab5fe7..07b2170 100644
--- a/Doc/lib/libmpz.tex
+++ b/Doc/lib/libmpz.tex
@@ -24,7 +24,7 @@
 below for an exact description). An mpz-number is printed like this:
 \code{mpz(\var{value})}.
 
-\renewcommand{\indexsubitem}{(in module mpz)}
+\setindexsubitem{(in module mpz)}
 \begin{funcdesc}{mpz}{value}
   Create a new mpz-number. \var{value} can be an integer, a long,
   another mpz-number, or even a string. If it is a string, it is
@@ -69,7 +69,7 @@
 
 An mpz-number has one method:
 
-\renewcommand{\indexsubitem}{(mpz method)}
+\setindexsubitem{(mpz method)}
 \begin{funcdesc}{binary}{}
   Convert this mpz-number to a binary string, where the number has been
   stored as an array of radix-256 digits, least significant digit first.