Update main.cpp

Nonce fix issue
Update global.h

nonce fix
Update README.md
Update miner.cpp

nonce fixes
Merged remote-tracking branch 'remotes/aero1/master'

Small tidy up to merged code to make function arguments const where possible. Added move of commandline struct to top of main.cpp to fix a compile error. Amended MaxNonce to be a static const to match primecoind sources.