set buffer size for instruction cache in cs_disasm() to @count if @count > 0. this avoids realloc() in cases where @count is pre-determined. thanks Dang Hoang Vu for the idea
avoid setting instruction cache size to @count when Capstone uses user-customized memory management, which might fail in resource scarce env such as kernel
cs_disasm(): make sure cache_size is smaller than INSN_CACHE_SIZE to avoid integer overflow in malloc()
tests: use cs_group_name() to print out group names in test_detail.c & test_detail.py