core.sh: prefer "command xxx" over "$(type -P xxx)"

command builtin help overriding local function (for example: curl is an executable and also a function name in core.sh).
Also use bash4 builtin error-handling function command_not_found_handle().
core.sh (log_notice_stack): use builtin double-brackets instead of match()

match function invokes grep.
sendspace: fix https

Fixes issue 1114.
uptobox (download): fix, upstream changed

Site uses Solvemedia CAPTCHAs now
Fixes issue 1110
rapidgator (login): fix parsing of account type, upstream changed

Fixes issue 1116
uptobox (download): fix wait regexp

Here I have:
<br /> <b><font color="red">Enter code above<br /><br />and wait</b><strong><span id="5pz1x7">45</span> seconds</font></strong>
uploadable_ch: file not found message fix
oboom (download): add missing filesize case
Merge branch 'master' into luckyshare

Conflicts:
	src/core.sh