LU-11380 llapi: add llapi_fid_parse() helper

LU-11380 llapi: add llapi_fid_parse() helper

Split the llapi_* FID handling functions to a separate file
rather than continually increasing the size of liblustrepai.c.

Add llapi_fid_parse() to parse a string to binary struct lu_fid.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I15abfaf888a5474d62feebab4e8db543ba3ebbe5
Reviewed-on: https://review.whamcloud.com/36184
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>