SBTarget::Attach(SBAttachInfo &) was changed to not be asynchronous back in...

SBTarget::Attach(SBAttachInfo &) was changed to not be asynchronous back in February and this affected Xcode's abililty to cancel an attach to process by name.

Added the ability to specify if an attach by name should be synchronous or not in SBAttachInfo and ProcessAttachInfo.

<rdar://problem/22821480>

llvm-svn: 249361