ola: Add a +nowarnings variant to work around issues with the new compiler

[nomis52@…]

The new compiler that comes with XCode 5 is failing with :

#warning Use of the header <ext/hash_map> is deprecated.

This variant disables fatal warnings (-Werror) so users can continue to build until the next release with the fixes is out.

[larryv (Lawrence Velázquez)]

Why don’t you just use --disable-fatal-warnings all the time? It is generally not useful to use -Werror for end-user builds.

[nomis52@…]

We want to detect potential bugs early. We took the decision as a project to fail on warnings so that we find out about the problem. It's been working well for us.

[ryandesign (Ryan Carsten Schmidt)]

We don't want users to encounter errors building. We should disable -Werror all the time. That's the decision we've taken as a project. :)

[cooljeanius (Eric Gallager)]

Cc Me!

[ryandesign (Ryan Carsten Schmidt)]

ola @0.9.2 fails to build on the 10.7 and 10.8 buildslaves, with this error:

clang: error: argument unused during compilation: '-pthread'

An unused argument would normally only be a warning, but -Werror is turning the warning into an error.

I've disabled the use of -Werror in r124835.