We have a minimum requirement of VS 2015 for Windows builds, which supports
the z length modifier for format specifiers. So we don't need SizePrintfMacros.h
any more, and can just use %zu and friends directly everywhere.

MozReview-Commit-ID: 6s78RvPFMzv

--HG--
extra : rebase_source : 009ea39eb4dac1c927aa03e4f97d8ab673de8a0e