Extended LLDB to handle blocks capturing 'self'

in an Objective-C class method.  Before, errors
of the form

error: cannot find interface declaration for '$__lldb_objc_class'

would appear when running any expression when
the current frame is a block that captures 'self'
from an Objective-C class method.

<rdar://problem/12905561>

llvm-svn: 172880