Removed "-Wno-deprecated" from COMPILE_FLAGS

This feature is new to GCC 4.4, while OpenBSD uses 4.2.1
Stop tracking generated files

* files, generated as side-effect of running ``configure'' script,
* files, generated by ``configure'' script (Makefile, config.h),
* ``telegram'' binary.

All these files are setup-dependent and differ between targets.
Don't tracked Makefile and config.h

Both files are generated by ``configure'' script. Given that they:

  1. may change after running ``configure'' and
  2. are setup-dependent

there's no need to track them anyway.
Added support for OpenBSD
Update ax_lua.m4

Updated ax_lua.m4 to current version from GNU Autoconf Archive's git
repository with additional patch to support OpenBSD.[1] Regenerated
``configure'' script. DOcumented changes.

---
[1] https://savannah.gnu.org/patch/index.php?8355
On OpenBSD `telegram` should be linked with '-lcurses'
Added "-Wno-deprecated-declarations" to COMPILE_FLAGS
When using libedit also search for curses
LUA_INCLUDE belongs to CPPFLAGS, not CFLAGS
Add /usr/local/include and /usr/local/lib to CPPFLAGS and LDFLAGS

This allows to avoid extra options for BSDs and strangle Linux systems, where
some libraries may be installed under "/usr/local" prefix.
Clean up and merge Linux and BSD instructions

 * Now BSDs don't require setting environment for configure.
 * No default Makefile any more.
Merged "openbsd-initial" branch