deprecate zmq_ctx_destroy in favor of zmq_ctx_term

in order to avoid logical collisions with pre-existing notions of context destruction in bindings (czmq, pyzmq).
move configure.in -> configure.ac

autotools warns that configure.in
should actually be named configure.ac
AM_CONFIG_HEADER -> AC_CONFIG_HEADERS

AM_CONFIG_HEADER raises an 'obsolete error' with automake 1.13.
Merge pull request #498 from minrk/zmq_ctx_term

deprecate zmq_ctx_destroy in favor of zmq_ctx_term
Merge pull request #499 from minrk/ac_header

Minor autoconf tweaks
Shortening the =-chars to make asciidoc work
Merge pull request #500 from haf/fixes/asciidoc-title

Shortening the =-chars to make asciidoc work
do not use EPROTO on platforms that do not have it
Merge pull request #501 from chazmcgarvey/conditional-eproto

do not use EPROTO on platforms that do not have it
Add size check on XSUB message sends

Ensures 0 length messages aren't being checked for subscribtion status on whatever data happens to be following the data pointer.
define a dummy EPROTO for platforms that don't use it

This accomplishes the same thing as 2e2ef7fd in a potentially cleaner way.
Merge pull request #502 from ianbarber/master

Add bounds check on upstream XSUB messages
Added tests/test_disconnect_inproc to .gitignore
Fix cmake not linking librt to perf-tools
Merge pull request #504 from o172/master

Adds tests/test_disconnect_inproc to .gitignore
Merge pull request #505 from arsenm/master

Fix perf-tools build on Linux with cmake
Merge pull request #503 from chazmcgarvey/define-dummy-eproto

define a dummy EPROTO for platforms that don't use it
Fix using wrong name for windows.h check in cmake
Merge pull request #506 from arsenm/master

Fix using wrong name for windows.h check with cmake
Removed heap allocation for in zmq_poll for small item sets

Until now, zmq_poll always allocates the poll items on the heap.
Now, small item sets, up to ZMQ_POLLITEMS_DFLT, are stack allocated
and only larger sets are allocated on the heap.