[PATCH] PR12214 - warn on suspicious self-compound-assignments

[Richard Smith]

Maybe tweak the diagnostic (for both this case and the normal self-assignment case) to:

  explicitly assigning value of variable of type %0 to itself

(Adding the 'value of' makes this message work better for the compound-assignment case.)

Other than that, LGTM

http://reviews.llvm.org/D3753