preproc.c: Turn off rmacro,exitmacro support

We've a problem in supporting [i]rmacro, exitmacro
facilities at moment.

In a sake of not holding new NASM release any longer these
directives are just marked as being "forbidden".

This allow us to not squash much changes in current source
code base but remain on a safe side same time.

Reviewed-by: Keith Kanios <keith@kanios.net>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
diff --git a/doc/changes.src b/doc/changes.src
index 8fc53f9..e48aa5d 100644
--- a/doc/changes.src
+++ b/doc/changes.src
@@ -12,11 +12,11 @@
 
 \b A number of enhancements/fixes in macros area.
 
-\b Support for arbitrarily terminating macro expansions \c{%exitmacro}.
-  See \k{exitmacro}.
+\#\b Support for arbitrarily terminating macro expansions \c{%exitmacro}.
+\#  See \k{exitmacro}.
 
-\b Support for recursive macro expansion \c{%rmacro}/\c{%irmacro}.
-  See \k{mlrmacro}.
+\#\b Support for recursive macro expansion \c{%rmacro}/\c{%irmacro}.
+\#  See \k{mlrmacro}.
 
 \b Support for converting strings to tokens.  See \k{deftok}.