TS-2269 regex_remap plugin does not deal with empty path's properly.

This is a problem when the request URL path is just '/', which inside
of ATS is an emptry string.

Review: leif
Added TS-2269.
TS-2254 On ARM arch, ink_atomic_increment returns wrong value

It should return the old value, before the increment. This is
consistent with how the other ink_atomic_increment implementation
works.

Review: leif
Added TS-2254.
TS-2189 Document proxy.config.http.cache.cluster_cache_local.

This is confusing for sure, in that it's actually an alternative to
controlling local caching via records.config. The intent, as far as I can
tell, is that you'd use this as an overridable configuration.
TS-2189 Document cluster-cache-local in cache.config
TS-2197

use HttpSM::main_handler to handle the client request stuff ranther
than directly call the HttpSM::state_read_client_request.

reenable the client_vc even if the ua_buffer_reader is not empty, or
else we may not perceive client_vc`s aborted.
DOC: Large update of cache architure.
doc: update cluster howto to for connections
Always forward SSH keys to VMs.
TS-2138 fix the bug that restarting ATS cause cache data loss if enable
native-AIO.
TS-2159: Force first log rotation at proxy.config.log.rolling_size_mb
Add missing line feed on warning message.
Quiet a benign compiler warning on OSX
small change to make eclipse happy
TS-2278: Cleanup of rfc5861 plugin
TS-1988 cquuc and cquup can have no values

When there is no remap phase, the unmapped URL does not get
populated. This means that cquuc and cquup can have no value,
so a "-" is logged. This happens, for example, with server
intercept plugins that do not pass through a remap phase.

This patch falls back on the original client URL in these
situations.
Added TS-1988
TS-2243 document exec_thread.affinity

document proxy.config.exec_thread.affinity, according to the code in
ocore/eventsystem/UnixEventProcessor.cc 160+

n.b.: I'm not documenting the default case, that treats every value that
is not 0, 2, or 3 as `1`. I couldn't find the words.

IMO, we should error out here, rather than potentially mis-interpreting
an admin's intent.
initial atscppapi commit