Avrdude for updating Prusa MK3 firmware.

Note that you ONLY need this special avrdude variant if you want to flash
Prusa MK3 firmware *AND additional languages*. If you want only English
then stock avrdude is enough.

Checkout, compile, rename to avrdude-prusa and tell OctoPrint-FirmwareUpdater
to use it.

NOTE: Needs OctoPrint-FirmwareUpdater with Prusa MK3 support
(which isn't released nor merged yet)
OctoPrint/OctoPrint-FirmwareUpdater#325

Differencies between this and stock avrdude:
* special serial command is needed to make Prusa MK3 hardware ready for
  programming external flash
* Prusa USB to serial converter is buggy  and doesn't like ';' character to be
  transmitted. Workaround for that is needed.

Changes taken from:
https://github.com/prusa3d/PrusaSlicer/tree/master/src/avrdude

Building:
libtoolize --copy --force
aclocal
autoconf
autoheader
automake -a -c
./configure --prefix=/usr --sysconfdir=/etc
make
mv avrdude avrdude-prusa

================================================

See the documentation file for the details.

The latest version of AVRDUDE is always available here:

  http://savannah.nongnu.org/projects/avrdude


Important environment variables for ./configure:
================================================

CPPFLAGS: C preprocessor flags (*not* "C++")

This is the place to put additional (non-standard) -I options into.
For example, if your Windows system has LibUSB-Win32 installed into
\\WINDOWS\ProgramFiles\LibUSB-Win32, use

CPPFLAGS=-I/WINDOWS/ProgramFiles/LibUSB-Win32/include

to tell configure where to search for the header files.  (The use of
forward slashes rather than backslashes can often simplify things.
Note that the Windows system services internally treat both the same.
It's only cmd.exe which requires backslashes as the directory
separator.)

LDFLAGS: Linker options

This is the place to make additional library locations known to the
linker.  To continue the above example, use

LDFLAGS=-L/WINDOWS/ProgramFiles/LibUSB-Win32/lib/gcc

to make the linker search for "libusb.a" in that directory.


Linux users: make sure the header files are installed
=====================================================

While many Linux distributions install the libraries needed by AVRDUDE
(libusb, libelf) by default, they leave out the corresponding header
files.  Consequently, the configure script won't find them, so these
libraries could not be used.

Usually, the packages with the header files (and static libraries) are
derived from the regular package name by appending "-devel".  Thus,
make sure you have "libusb-devel" and "libelf-devel" installed before
running the configure script.  (Same goes for libftdi.)