Previous to this patch each time a bytes object was referenced a new
instance (with the same data) was created.  With this patch a single
bytes object is created in the compiler and is loaded directly at execute
time as a true constant (similar to loading bignum and float objects).
This saves on allocating RAM and means that bytes objects can now be
used when the memory manager is locked (eg in interrupts).

The MP_BC_LOAD_CONST_BYTES bytecode was removed as part of this.

Generated bytecode is slightly larger due to storing a pointer to the
bytes object instead of the qstr identifier.

Code size is reduced by about 60 bytes on Thumb2 architectures.

This patch gets full function argument passing working with native
emitter.  Includes named args, keyword args, default args, var args
and var keyword args.  Fully Python compliant.

It reuses the bytecode mp_setup_code_state function to do all the hard
work.  This function is slightly adjusted to accommodate native calls,
and the native emitter is forced a bit to emit similar prelude and
code-info as bytecode.

Currently supports only x64 and Thumb2 archs.

Previous to this patch, a big-int, float or imag constant was interned
(made into a qstr) and then parsed at runtime to create an object each
time it was needed.  This is wasteful in RAM and not efficient.  Now,
these constants are parsed straight away in the parser and turned into
objects.  This allows constants with large numbers of digits (so
addresses issue #1103) and takes us a step closer to #722.

This allows an exception to propagate correctly through a finally
handler.

Addresses issue #1022.

Viper can now do the following:

def store(p:ptr8, c:int):
    p[0] = c

This does a store of c to the memory pointed to by p using a machine
instructions inline in the code.

Part of code cleanup, working towards resolving issue #50.

This way, the native glue code is only compiled if native code is
enabled (which makes complete sense; thanks to Paul Sokolovsky for
the idea).

Should fix issue #834.