Update to 1.2.12. Add webp support. Update LICENSE (see below).

While here, remove png/tiff/jpeg includes from buildlink3.mk
since they are hidden by the library (library not linked against
them, headers not included in public headers). Recursive bump
coming next.

1.2.12:
Sam Lantinga - Thu Jan 19 23:18:09 EST 2012
* Fixed regression in 1.2.11 loading 8-bit PNG images with libpng

1.2.11:
Sam Lantinga - Sat Jan 14 17:54:38 EST 2012
* Fixed loading 8-bit PNG images on Mac OS X
Sam Lantinga - Sat Dec 31 09:35:40 EST 2011
* SDL_image is now under the zlib license
Michael Bonfils - Mon Nov 28 21:46:00 EST 2011
* Added WEBP image support
Thomas Klausner - Wed Jan 19 19:31:25 PST 2011
* Fixed compiling with libpng 1.4
Sam Lantinga - Mon Jan 10 12:09:57 2011 -0800
* Added Android.mk to build on the Android platform
Sam Lantinga - Mon May 10 22:42:53 PDT 2010
* Fixed loading HAM6 images with stencil mask
Mark Tucker - Fri, 27 Nov 2009 12:38:21 -0500
* Fixed bug loading 15 and 16 bit BMP images

(wiz)