The Google style guide is neutral on whether there should be a
space before the protocol list in an Objective-C @interface or
@implementation.
The majority of Objective-C code in both Apple's public
header files and Google's open-source uses a space before
the protocol list, so this changes the google style to
default ObjCSpaceBeforeProtocolList to true.
Test Plan: make -j12 FormatTests && ./tools/clang/unittests/Format/FormatTests