Add 3 functions to utils_memory for getting some usage info of hugepages.

get_num_anon_huge_pages(pid) : get the anonhugepages' usage amount of a progress
get_num_huge_pages_free() : get the number of free hugepages
get_num_huge_pages_rsvd() : get the number of rsvd hugepages
with open() as f seems not support in old version of python like python 2.4.  So maybe we'd better to not use it. But agree with you about that we should close it after we use it.