x11: shavite and echo from sp (now ok on win32)

Previous echo commit was only increasing linux performance, and reducing
windows perf compared to the 1.4.9, this one seems to give at least
the 1.4.9 on windows, and the same on linux...

Shavite optimisation seems ok on both (use now 64 registers)

the launch_bounds will force the number of registers, so remove specific
Makefile rules on linux...

manual "cherry pick" with fixed line endings and some adaptations
vstudio: clean the project file
api: fix includes after a test on mingw (cpuminer)
hashrate: ignore first loop speed (often lowered)
x11: switch to intensity 20 for SM>=5.2 750+970