Cross-compiling update.

[Amar Takhar]

This is more work than I was expecting I was nearly done but (re)discovered that 
keyword-gen uses libntp!

I want to avoid building libntp twice if the host and target are the same so I 
need to refactor a little.  I have variants working in waf I'll tackle this 
tomorrow.

I'll also hookup cross-compiling under buildbot so we can catch as many 
architecture issues as possible during compile-time.

I also discovered one quirk by accident when compiling for ARM:

  37:#error libntp supplied mktime()/timegm() do not support 64-bit time_t

I wonder how often users will hit that?


Amar.