Make all the headers public.

Until someone mentions which headers are supposed to be private, this will probably be how it's done.
TargetConditionals is a system header. Include it as such.
Change CGColorWithSVGColor to CreateCGColorWithSVGColor. I did this because I don't know if Cocoa's autorelease will work on a CGColorRef and to make the static analyzer happy.
Make the iOS version of CreateCGColorWithSVGColor return a retained CGColor like the Mac version.
Change the define of SVGImageRef to a typedef.
Better error reporting code, hopefully.
Merge branch 'master' into arc

Conflicts:
	SVGKit-OSX.xcodeproj/project.pbxproj
	Source/DOM classes/Unported or Partial DOM/SVGGradientElement.m
	Source/Parsers/SVGKParser.m