[Rd] Two bugs showing up mostly on SPARC systems

[Radford Neal]

In testing pqR on Solaris SPARC systems, I have found two bugs that
are also present in recent R Core versions.  You can see the bugs and
fixes at the following URLs:

  https://github.com/radfordneal/pqR/commit/739a4960a4d8f3a3b20cfc311518369576689f37

  https://github.com/radfordneal/pqR/commit/339b7286c7b43dcc6b00e51515772f1d7dce7858

The first bug, in nls, is most likely to occur on a 64-bit big-endian
system, but will occur with low probability on most platforms.  

The second bug, in readBin, may occur on systems in which unaligned
access to data more than one byte in size is an error, depending on
details of the compiler.  It showed up with gcc 4.9.2 on a SPARC
system. The fix slightly changes the error behaviuor, signaling an
error on inappropriate reads before reading any data, rather than
after reading one (but not all) items as before.

   Radford Neal