make blockchain-opencl non-plug

This fixes building on systems without OpenCL (with non-opencl make
targets used).

Compile error was:
$ make linux-x86-64i
...
gcc -c -Wall -Wdeclaration-after-statement -O2
-fomit-frame-pointer -I/usr/local/include -I/usr/include/nss
-I/usr/include/nspr -DHAVE_NSS -DHAVE_GMP -DHAVE_CRYPT -DHAVE_DL
-DUSING_ICC_S_FILE -funroll-loops opencl_blockchain_fmt_plug.c
In file included from opencl_blockchain_fmt_plug.c:29:0:
common-opencl.h:22:19: fatal error: CL/cl.h: No such file or directory
compilation terminated.
make[1]: *** [opencl_blockchain_fmt_plug.o] Error 1
make[1]: Leaving directory `/home/src/john/src'
make: *** [linux-x86-64i] Error 2
fix build problem caused by blockchain format
fix function prototype in mscash2-opencl format
fix OMP build problem
Fix build problems on XOP systems
Fix build problems on XOP systems
some "dangerous" optimizations in the blockchain format
increased PW length of mscash2 from 27 to 125 and username length from 22 to 128
Merge remote-tracking branch 'origin/bleeding-jumbo' into memdbg