Add size field to library load event (MI)

Summary:
(This revision supersedes the abandon: http://reviews.llvm.org/D9716)
Size field is used to let the debugger attribute an address to a specific library when symbols are not available. 
For example:
	OpenGLESApp4.app!Cube_draw() Line 74	C
 	OpenGLESApp4.app!-[GameViewController glkView:drawInRect:](GameViewController * self, SEL _cmd, GLKView * view, CGRect rect) Line 89	C++
 	GLKit!<redacted>	
 	QuartzCore!<redacted>	
 	QuartzCore!<redacted>	
 	QuartzCore!<redacted>	
 	QuartzCore!<redacted>	
 	QuartzCore!<redacted>	
 	UIKit!<redacted>	
 	UIKit!<redacted>	
 	UIKit!<redacted>	
 	UIKit!<redacted>	
 	FrontBoardServices!<redacted>	
 	CoreFoundation!<redacted>	

Patch from paulmay@microsoft.com

Reviewers: ChuckR, abidh, ki.stfu

Subscribers: greggm, lldb-commits

Differential Revision: http://reviews.llvm.org/D11574

llvm-svn: 244573