Fix bug that prevented DEBUG being set for ext/
Fix bug that prevented DEBUG being set for ext/

Changes add_dr_defines() to a macro to fix a bug where for 64-bit debug
builds, all of ext/ failed to have the preprocessor define DEBUG set.

Review-URL: https://codereview.appspot.com/261410043

AmesianX/dynamorio,code4bones/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,code4bones/dynamorio,code4bones/dynamorio,AmesianX/dynamorio