M100 had numerious changes and quit working. Part of the problem is
the overloading of the SERIAL_PROTOCOL functions. Also, some of the
address arithmatic was changed to use char *ptr and passing ptr into the
SERIAL_PROTOCOL functions caused them to try to print a string instead
of a number. M100 is working again. Let's keep it that way!
M100 has been expanded to now have a function int
free_memory_is_corrupted() that can be called from other code to see if
the free space is still contiguous. It may make sense to add a flag to
control its verbose nature but right now, the extra chit chat is very
helpful to know int free_memory_is_corrupted() is doing the right thing
and what it found at various points when it was called. A 'Show &
Tell' is coming up with int free_memory_is_corrupted().
This is an update of MarlinDev PR #196.
G20/21: support for switching input units between millimeters and
inches.
M149: support for changing input temperature units.
In support of these changes, code_value() and code_value_short() are
replaced with an array of functions which handle converting to the
proper types and/or units.
