Somebody (accidentally) removed the instructions for updating libevent releases in OMPI, so replace them with at least an outline on how to do it.

This commit was SVN r28349.

opal/mca/event/OMPI_LIBEVENT_README.txt

@@ -0,0 +1,26 @@
+* create a new subdirectory opal/mca/event/libeventxxxx
+
+* copy these files from the current component to the new directory
+	autogen.subdirs
+	configure.m4
+	libeventxxxx_component.c
+	libeventxxxx_module.c
+	libeventxxxx.h
+	Makefile.am
+	opal_check_visibility.m4
+
+* update the libevent version numbers in the above files by doing a global replace
+
+* expand the libevent tarball into the new directory under a subdirectory named "libevent"
+
+* copy libeventxxxx/libevent/opal_rename.h to the new libeventyyyy/libevent and change the version number in the symbol renames
+
+* rename libevent/configure.in to libevent/configure.ac
+
+* edit the following files per their counterparts in the current version
+	libevent/configure.ac
+	libevent/Makefile.am
+	libevent/include/event2/event.h
+	libevent/include/event2/thread.h
+	libevent/log-internal.h
+	libevent/log.c