man: add filelist option to system-readahead documentation

Signed-off-by: Alison Chaiken <alison_chaiken@mentor.com>
readahead: add switch to specify list of files used for pack

Signed-off-by: Alison Chaiken <alison_chaiken@mentor.com>
readahead: mark array of file descriptors created from filelist

Signed-off-by: Alison Chaiken <alison_chaiken@mentor.com>
readahead: create pack from specified file list
readahead: support for file-size-min feature