build: add OBJC makefile var

Overrides the Objective-C compiler that is used. Defaults to $(CC).
Prepare for making releases, add uv_version/uv_version_string API
Update AUTHORS and .mailmap
2013.03.25, Version 0.10.2 (Stable)

This is the first officially versioned release of libuv. Starting now
libuv will make releases independently of Node.js.

Changes since Node.js v0.10.0:

* test: add tap output for windows (Timothy J. Fontaine)

* unix: fix uv_tcp_simultaneous_accepts() logic (Ben Noordhuis)

* include: bump UV_VERSION_MINOR (Ben Noordhuis)

* unix: improve uv_guess_handle() implementation (Ben Noordhuis)

* stream: run try_select only for pipes and ttys (Fedor Indutny)

Changes since Node.js v0.10.1:

* build: rename OS to PLATFORM (Ben Noordhuis)

* unix: make uv_timer_init() initialize repeat (Brian Mazza)

* unix: make timers handle large timeouts (Ben Noordhuis)

* build: add OBJC makefile var (Ben Noordhuis)

* Add `uv_version()` and `uv_version_string()` APIs (Bert Belder)
Now working on v0.10.3
include: remove extraneous const from uv_version()

Fixes the following warning:

  include/uv.h:236:30: warning: type qualifiers ignored on function
  return type [-Wignored-qualifiers]
   UV_EXTERN const unsigned int uv_version(void);
doc: update README, s/OS/PLATFORM/

Commit a9740c9 changed the name of the OS var to PLATFORM but forgot to
update the README.
build: simplify .buildstamp rule
Merge remote-tracking branch 'origin/v0.10'