Remove useless open modes

Previously, the machinery that detected these was only enabled in
optimized builds. We're expanding it to work in code built with -O0, as
well. Thus, we now get compile-time warnings about these calls (which
get turned into errors by -Werror).

Bug: 12231437
Test: Builds without warnings about useless mode bits in calls to open()
Change-Id: Icb1bc5f0a7941bb90d8581d6c3bde7cc076f3e01