The non-use of the intptr_t typedef probably is a systematic error...lather, rinse, repeat.
Sourceforge's mirror system doesn't even work properly in a web browser. The automatic mirror selection pointed me at the nearest dead mirror. Even with that manually overridden, the cloudfront frontend is choking every few minutes. (I am intentionally downloading the archives rather than the installer, to allow proper backing up of the full install archive set locally.)
With this much of a version jump, I'll have to test to see whether current binutils works with the last-known-good MingW32 GCCs (4.3.3 and 4.2.1; later ones in the 4.x series die on syntax errors in compiler-generated assembly for just about anything significant, e.g. libpng). I'm assuming, since TDM GCC 5.1.0 builds LCS, that it is "sane".