add extra verbiage about hardware problems to verify error message, hopefully this will cut down on the number of bogus bug reports

tweaks to the MD5 routines; they need to be exported when building a windows DLL since the seekable stream decoder in libOggFLAC secretly uses them

make encoder encode the blocksize and sample rate in the frame header whenever possible, regardless if subset is specified or not

add more informative error info for some common errors; also, no not exit with error when decoding to stdout and writing return EPIPE