putlocker (download): it seems that video streaming content has always the "Download File" button

Original file can be downloaded, don't need to distinguish "online streaming" and "direct download" anymore.
core.sh (grep_block_by_order): use "grep -c" instead of "sed + tr"

This is faster!
plowup: add sanity check, check if returned URL contains \r
docs (plowdown.1): enhance documentation for --captchaprogram
4shared (upload): quick upload fix
4shared (upload): fix, forget to drop temp debug
download.sh (mark_queue): fix unmarked url (if it contains backslash characters)
mediafire (login): send referrer so website does not refuse login
mediafire (download, probe): small rewrite to enhance features

- new functions "mediafire_extract_id" and "mediafire_is_file_id"
- fix detection of direct download links
- add error message when file links are given to plowlist or
folder links are given to plowdown

Note: Detection of folder vs. file links is quite fragile. It relies
on folder IDs to consist of exactly 13 digit/letters. This is true
for all links I found but need not be a general fact.
mediafire: add probe support
dl.free.fr (download + probe): upstream modified, fix dead link detection
mediafire (upload): copy a Mediafire hosted file into own account

Users with an account may add a file to their own account instead
of downloading it. This is implemented for plowup as a special
kind of remote upload which only allows Mediafire URLs and will
return a dummy link ("#") as the website does not return the new
download link.
turbobit (login): deal with optional captcha
uptobox: add probe support
zalaa (probe): minor, simplify code
cramit (download): fix anonymous download

+ add probe support
1fichier (download): detect deleted files
letitbit (upload): fix, upstream modified
1fichier (download): fix, detect more deleted files
1fichier (download): detect forced delay between two downloads