Rename macros TONATIVE_BOOL* and TOSTRING_BOOL to *_DEFAULT

These macros do not always take a boolean value;
correction per comment by Philipp (pneubeck@):
https://codereview.chromium.org/232563003/#msg30

R=haraken

Review URL: https://codereview.chromium.org/242223004

git-svn-id: svn://svn.chromium.org/blink/trunk@171925 bbb929c8-8fbe-4397-9dbb-9b2b20218538