Addresses #1510.

Saves a few bytes of code space and eliminates need for rot_two
bytecode (hence saving RAM and execution time, by a tiny bit).

r7 may be needed to set up code state, so it must be loaded before the
set-up function is called.

ViperTypeError now includes filename and function name where the error
occurred.  The line number is the line number of the start of the
function definition, which is the best that can be done without a lot
more work.

Partially addresses issue #1381.

Otherwise it can be very hard to track down bugs.

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 allows to do "ar[i]" and "ar[i] = val" in viper when ar is a Python
object and i and/or val are native viper types (eg ints).

Patch also includes tests for this feature.

The code was apparently broken after 9988618e
"py: Implement full func arg passing for native emitter.". This attempts to
propagate those changes to ARM emitter.

Addresses issue #1226.

This fixes a long standing problem that viper code generation gave
terrible error messages, and actually no errors on pyboard where
assertions are disabled.

Now all compile-time errors are raised as proper Python exceptions, and
are of type ViperTypeError.

Addresses issue #940.

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.

This implementation is smaller (in code size) than #1024.

This is a temporary fix.

Saves around 230 bytes on Thumb2 and 750 bytes on x86.

Saves 116 bytes for stmhal and 56 bytes for cc3200 port.

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 makes the code (more) compatible with the C99 standard.

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

See issue #699.

Saves 24 bytes in bare-arm.

Native code has GC-heap pointers in it so it must be scanned.  But on
unix port memory for native functions is mmap'd, and so it must have
explicit code to scan it for root pointers.

This allows to directly load a Python object to the Python stack.  See
issue #722 for background.

Addresses issue #1022.

This patch makes the MICROPY_PY_BUILTINS_SLICE compile-time option
fully disable the builtin slice operation (when set to 0).  This
includes removing the slice sytanx from the grammar.  Now, enabling
slice costs 4228 bytes on unix x64, and 1816 bytes on stmhal.