to capture chars at UART at 250000 baud.

If the stepper ISR takes too long, chars are lost which leads to serial
communication errors like "Line number not +1" or "Wrong checksum". In
worst case, the printer can even do crazy moves.

With this changes, UART interrupts are handled inside the stepper ISR.
This way, no chars should be lost.

Endstop interrupt refinement

At the start of a move, check if the endstops are already triggered.
The 'change' interrupts will not see a change if already triggered.

Ensure smooth print moves even with LCD enabled

Re-follow the PR #4634 (Set language display charset in language.h)

lcd_update can take so much time that the block buffer gets drained if
there are only short segments. This leads to jerky printer movements for
example in circles and a bad print quality.

This change implements a simple check: Only if the block currently
executed is long enough, run lcd_update.
This also means the printer will not show actual values on the LCD nor
will it respond to buttons pressed. A option that keeps the menu
accessible is also available.
Aditionaly, slow down if a block would be so fast that adding a new
block to the buffer would take more time. In this case, the buffer would
drain until it's empty in worst case.

Added CMake support

K8200: Example configuration back in sync

Endstop interrupts followup

- Fix typos, verbiage
- Fix naming of `setup_endstop_interrupts`
- Some formatting, indentation, spacing

Introduce endstop interrupts

Configuration.h: back in sync, new features configured
Configuration_adv.h: back in sync, new features configured
README.md: text updated

Update to Danish language 10/11-2016

This allows M104 to pass the F and B parameters to enable autotemp as well

Advance has nothing todo with Z_AXIS, strange copy&paste error?

Update Japanese translation

Replace const bool with #define for consistency

Only adjust spacing

Printer Stats / Completed prints line doesn't fit in display (when german)

Save some cycle inside the planner

Fix DIRECT_MIXING_IN_G1 to preserve the previous mix

bump -std in Makefile to c++11

Fix G30 with limits, print correct probe XY

still a few bytes bigger than with arduino but nothing major

needed for constexpr

If ENDSTOP_INTERRUPTS_FEATURE is enabled this tries to set up interrupt routines
for all used endstop pins. If this worked without errors, `endstops.update()` is called
only if one of the endstops changed its state.

The new interrupt routines do not really check the endstops and react upon them. All what they
do, is to set a flag if it makes sense to call the endstop test we are used to.

This can be used on:
* ARM (DUE) based boards - all pins can raise interrupts,
* RAMPS - all 6 endstop pins plus some other on EXT-2 can raise interrupts,
* RAMPS based boards - as long the designers did not change the pins for the endstops or at least left enough,
* all boards, if there are enough pins that can raise interrupts, and you are willing/able to swap with pins dedicated to other purpose.

planner.h:
fan speed is used to set integer variables, so no need for long.
Basicaly a byte should be enough for all the fan things, as it's 0-255?

planner.cpp:
Save some float multiplications.
We could squeeze out even more by defining feedrate_percentage,
saved_feedrate_percentage and flow_percentage as float instead of int.
Everytime they are used in the time-critical planner, they are casted to
float and multiplied by 0.01. Not done jet, as they are used in LCD menu
functions I don't know well enough.

Store mix factors as reciprocals and multiply

Extended host support: M155 Auto temp report, M115 capabilities

Follow up the PR #5167 (Add Turkish Language) again, etc

Remove useless line from stepper ISR

Megatronics 3.0 has no SD-Card detect