per group var_count and attr_count 16bit --> 64bit
 per group var_count and attr_count --> 32bit
- var and attribute counts and ids are 32bit everywhere
- BP format version changed to 2
old read functions to accept BP format version 2
Modify bp version to 2 in test suite reference output files
bpdump prints BP file format version (at the beginning)
Increased hash table size. In read, calculated from number of variables. In write, 100->500
many_var test: increased buffer size for testing 200k variables
Merge branch 'master' into varid64