Release 2.0
-D doesn't build on OSX Lion
Merge pull request #47 from PatrickHeneise/master

-D doesn't build on OSX Lion
Tweaked Makefile for building on OS X

Fix for 2.x
Posterize option
Restored include for USE_SSE macro
C89
Deleted unused struct
USE_SSE opt-in
Simplified optimization flags
SunOS compatibility

Fixes #49
Add include directories conditionally to avoid warnings
PIC in DLL
Fixed calling of sub-makefiles with flags
Markdown formatting
Manual updates
Discourage use of libpng 1.2
convert pointer to integer before performing arithmetic

fixes mempool issues on platforms where sizeof(struct mempool) & ALIGN_MASK != 0
Tell libpng to expand all types to support RGB+tRNS images
Version bump