py: Remove obsolute function declaration.
py: Use shorter, static error msgs when ERROR_REPORTING_TERSE enabled.

Going from MICROPY_ERROR_REPORTING_NORMAL to
MICROPY_ERROR_REPORTING_TERSE now saves 2020 bytes ROM for ARM Thumb2,
and 2200 bytes ROM for 32-bit x86.

This is about a 2.5% code size reduction for bare-arm.
py: Fix order-only dependencies in mkrules.mk and py.mk.

Currently compilation sporadically fails, because the automatic
dependency gets created *during* the compilation of objects.

OBJ is a auperset of PY_O and the dependencies apply to all objects.

Signed-off-by: Sven Wegener <sven.wegener@stealer.net>