gcc 6.1.1 warns when indentation is misleading, and in this case the
formatting of the code really is misleading. So adjust the formatting
to be clear of the meaning of the code.
acoshf, asinhf, atanhf were added from musl. mathsincos.c was
split up into its original, separate files (from newlibe-nano-2).
tan was added.
All of the important missing float functions are now implemented,
and pyboard now passes tests/float/math_fun.py (finally!).