Fixes #4100: Move r30269 to v1.7 branch (readme update for g95+netbsd-6+amd64)

---svn-pre-commit-ignore-below---

r30269 [[BR]]
Add note about what Paul Hargrove discovered abotu g96 on the NetBSD-6
AMD64 platforms:

    http://www.open-mpi.org/community/lists/devel/2014/01/13748.php

cmr=v1.7.4:reviewer=rhc:subject=README update for g95+NetBSD-6+AMD64
Fixes #4103: Move r30274 to v1.7 branch (fix netbsd use of -laio)

---svn-pre-commit-ignore-below---

r30274 [[BR]]
Patch submitted by Paul Hargrove to fix NetBSD compile with -laio.

NetBSD puts the AIO functions in -lrt, vs. the usual libc.  So we
need the fbtl/posix configure.m4 to test for -lrt properly.

Reviewed by Jeff Squyres.

cmr=v1.7.4:reviewer=ompi-rm1.7:subject=Fix NetBSD use of -laio
Fixes #4109: Move r30276 to v1.7 branch (fix mca base var to not pass union by value)

---svn-pre-commit-ignore-below---

r30276 [[BR]]
Remove a sketchy use of asprintf() passing a union by value.

The original code was passing a union by value, and doing odd things
on Solaris/SPARC (where "odd" rhymes with "SIGBUS").  Replace it with
an exploded switch/case block for all the enum values.  Also use the
string literals so that we get compiler checking of the format string
vs. the type of the actual arguments.

cmr=v1.7.4:revier=hjelmn:subject=Fix MCA base var to not pass union by value