2. Add flag INTERNAL_LIBM to mpconfigboard.mk files to signal using lib/libm.
3. Fix floating-point warnings in lib/libm
4. Turn off -finline-limit, no longer needed due to 1.
5. Add explicit flags for SPI_FLASH_FILESYSTEM and INTERNAL_FLASH_FILESYSTEM
to mpconfigboard.mk files, so they don't need to know the name of the .c file
that implements those. Makefile takes care of checking the flags and including
the right files.
These implementations are incorrect (eg f2d and d2f don't handle special
values like 0.0) and proper versions can be provided by libgcc (or
equivalent depending on the toolchain).
libgcc is now linked with the stmhal port so that library will provide
these functions from now on.
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!).
Top-level lib directory is for standard C libraries that we want to
provide our own versions of (for efficiency and stand-alone reasons).
It currently has libm in it for math functions.
Also add atanf and atan2f, which addresses issue #837.
