SSE2 optimizations are used by default on 64-bit platforms. By no longer explicitly enabling SSE2 on 64-bit GCC, we can more easily enable other optimizations (e.g. AVX) without worrying about them being overridden by the SSE2 flags.
Although it's enabled by default in gcc (should be, anyway!), we're
being explicit here for 64-bit x86 platforms here also. This matches the
old behavior.
- `--enable-official-branding` implies `MC_OFFICIAL` (no need to specifically set it)
- `--enable-official-vendor` can be used to set `MC_OFFICIAL` on builds without `--enable-official-branding` that should still be considered official release versions.
- `MC_OFFICIAL` implies `--enable-release`, meaning `DEVELOPER_OPTIONS` isn't set
- `MC_OFFICIAL` makes `nsXULAppInfo.getIsOfficial` return `true`
- `MC_OFFICIAL` makes `AppConstants.MOZILLA_OFFICIAL` (for compatibility in extensions) and `AppConstants.MC_OFFICIAL` return `true`
- Optional, for the time being: `MOZILLA_OFFICIAL` is still present in some places in case someone wants to build a Mozilla-alike official application and has the rights and necessary keys to use Mozilla-official third-party services. This must always be combined with `MC_OFFICIAL` to have a sane combination of defines. This may be removed in the future.