preproc: add dummy %pragma directive

In future versions of NASM we will presumably have "real" pragmas; add
dummy support for the %pragma directive for forward compatibility.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/doc/changes.src b/doc/changes.src
index 682c7d1..61b6511 100644
--- a/doc/changes.src
+++ b/doc/changes.src
@@ -35,6 +35,10 @@
    included in a shipping product; it is included for completeness
    only.
 
+\b Add the \c{%pragma} preprocessor directive for forward
+   compatibility with future versions of NASM.  At this time no pragmas
+   are implemented and this is merely a dummy directive.
+
 \S{cl-2.12.02} Version 2.12.02
 
 \b Fix preprocessor errors, especially \c{%error} and \c{%warning},