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
We normally use open($file_path) and read() to get the information for localhost. This can ignore the influence of command output is different in different system. For example, some time the output of grep include some console control characters and that will influence the following string deal code.