require() has observable side effect - errno is reset

[GoogleCodeExporter]

Loading a module to deal with errors can cause us to appear to have no error, 
because the C errno global is affected by the loading of the module (e.g. via 
gpsee_loadModule in gpsee_modules.c)

We should cache and restore errno so that pending errors can be properly 
reported by dynamically-loaded modules.

Original issue reported on code.google.com by i...@realtime-realty.com on 13 Apr 2011 at 3:19