More efficient sizeof() for complex types

Remarkably, this was originally the main bottleneck in the
cache-friendly transpose algorithm for small complex matrices.
Cache-friendly transpose algorithm
WINDOWS: fix memory bug introduced by #3078
Fix #2525
Merge pull request #3231 from staticfloat/master

Fix #2525
Improve and simplify blocksize calculation in transpose

This also yields better scaling.
Merge pull request #3219 from timholy/transposecf

Cache-friendly transpose