Add shell script to automatically build stmhal/ for all pyboards.
objtype: Work around stupid strict aliasing check.
py, unix: Make "mpconfig.h" be first included, as other headers depend on it.

Specifically, nlr.h does.
unix,stmhal: Make "mpconfig.h" be first included, as other headers depend on it.
bare-arm, qemu-arm: Make "mpconfig.h" be first included, as other headers depend on it.
stmhal: Add documentation for DAC and Timer classes.
Merge branch 'master' of github.com:micropython/micropython
unix-cpy: Put mpconfig.h before all other headers.