Use tabs for leading whitespace and spaces for continuation lines.
Besides that inconsistent whitespace looks odd, it causes unnecessary
merge conflicts.
Since commit b5cc61b3317e "fix critical section handling", there are two
versions of enable_irq, enable_irq(void) as used by queue.c and
enable_irq(int primask) as used by usbd_gs_can.c. As a consequence
interrupts might be re-enabled too early in case of nested disable calls.
To prevent this, declared enable_irq as void, since it doesn't accept an
argument and add restore_irq which requires an argument and adjust users
of it.
Avoid using <assert.h> because the standard assert() pulls in
fprintf and its of dependencies, as well as including __FILE__:__LINE__
strings for each assert() call. All this has an unacceptable memory
cost, as well as being useless since there is nothing to printf *to*.
Currently assert_basic() was added to check calloc() return values;
in case of failure we simply halt the core with BKPT(0). This could be
improved and refined.
