Remove an ugly hack that was meant to eliminate the breakpoint ambiguity
between a block assignment and the entry of the block function. In reality
this wouldn't work anyway because blocks are predominantly created
on-the-fly inside of an ObjC method invocation.
The proper fix for the ambiguity is to use -gcolumn-info to differentiate
the breakpoints.

This is expected to break some block-related darwin-gdb tests.

rdar://problem/14039866