added \iflabelundefined

--- a/doc-src/iman.sty	Thu Mar 24 15:23:02 1994 +0100
+++ b/doc-src/iman.sty	Thu Mar 24 16:12:42 1994 +0100
@@ -7,6 +7,10 @@
 
 \let\ts=\thinspace
 
+%usage: \iflabelundefined{LABEL}{if not defined}{if defined}
+\newcommand{\iflabelundefined}[1]{\@ifundefined{r@#1}}
+
+
 %%%INDEXING  use sedindex to process the index
 %index, putting page numbers of definitions in boldface
 \newcommand\bold[1]{{\bf#1}}