[jit] Remove references to unused llvm.invariant.start/end intrinsics.
Fixes :

https://bugzilla.xamarin.com/show_bug.cgi?id=16021
https://bugzilla.xamarin.com/show_bug.cgi?id=12754

Resolves:

http://lists.ximian.com/pipermail/mono-list/2013-June/050008.html

A reference to the variable bufsize, local to the else-if block was being passed to the function setsockopt hence the properties ReceiveBufferSize & SendBufferSize were being set to garbage on the Socket class. This could and did have a SERIOUS performance hit on socket communication. It is not inconceivable that people would try to increase the buffer sizes and inadvertently reduce the buffer sizes considerably. The resulting effect would possibly only have been noticed when communicating large block of data.

Narinder Claire
narinder.claire <<at>> gmail.com
Merge remote-tracking branch 'upstream/master'