remove most of the USE_SCRYPT defines

still won't compile unless configured with the --enable-scrypt option.
yacminer-yacminer.o: In function `rebuild_hash':
c:\build/yacminer.c:3349: undefined reference to `scrypt_regenhash'
removed autogenerated files and default enable scrypt

modify configure.ac to default to enable scrypt.
YACMiner 3.4.0-yac2

Major update - includes new parameters for fine-tuning YACoin mining
--buffer-size
--rawintensity
see the SCRYPT-README for details on these settings.
Minor changes include
Network difficulty line only shows up when it changes
fix for GPU fan going to 85% when saving and using a conf file
cgminer.conf should now be yacoin.conf (rename your file if you use it!)
Rewrote README as a .md file and updated SCRYPT-README to be more YACoin
specific