.luacheckrc: Ignore currently-unclean files unless env var PROSODY_STRICT_LINT=1

.luacheckrc: Fix whitespace

GNUmakefile: Add 'lint' target

util.iterators: Add join() method and tests

Merge 0.10 -> trunk

MUC: Restore status codes on presence sent to occupant when their affiliation changes (thanks jonasw)

Merge 0.10 -> trunk This commit intentionally drops changes from c2b99fa134b3 and 8da11142fabf which are based on older MUC code.

MUC: Allow the number of messages sent by default to be configured (fixes #397)

MUC: Import revised, more comprehensive patch for 8da11142fabf (#345)

muc: Allow clients to change multiple affiliations or roles at once (#345) According to XEP-0045 sections 9.2, 9.5 and 9.8 affiliation lists and role lists should allow mass-modification. Prosody however would just use the first entry of the list and ignore the rest. This is fixed by introducing a `for` loop to `set` stanzas of the respective `muc#admin` namespace. In order for this loop to work, the error handling was changed a little. Prosody no longer returns after the first error. Instead, an error reply is sent for each malformed or otherwise wrong entry, but the loop keeps going over the other entries. This may lead to multiple error messages being sent for one client request. A notable exception from this is when the XML Schema for `muc#admin` requests is violated. In that case the loop is aborted with an error message to the client. The change is a bit bigger than that in order to have the loop only for `set` stanzas without changing the behaviour of the `get` stanzas. This is now more in line with trunk, where there are separate methods for each stanza type. References: #345