i#1448 config failure: allow duplicate -code_api options
i#1448 config failure: allow duplicate -code_api options

Fixes a bug where passing -code_api and -c to drrun resulted in a confusing
failure and error message.

Fixes #1448

Review-URL: https://codereview.appspot.com/248640043

code4bones/dynamorio,bl4ckic3/dynamorio,bl4ckic3/dynamorio,daksunt/dynamorio,bl4ckic3/dynamorio,code4bones/dynamorio,AmesianX/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio,daksunt/dynamorio,code4bones/dynamorio,code4bones/dynamorio,daksunt/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio,daksunt/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,daksunt/dynamorio,code4bones/dynamorio