Protect MarlinSerial against interrupts
by shielding the CRITICAL_SECTIONs

Now with a test if RX_BUFFER_SIZE is in the required range.
Code in peek() and read() is now optimized for readability and showing the similarity between the two.

Maybe a bit overprotected in checkRx() and store_char(), but now some days without detected errors from this source.

more suitable display format for delta printer

Repair N in ADVANCED_OK

Rc bug fix

Replace the "ok" in M280, M301, M304, M851 with output not including …

Drop the experimental Configurator

Sanity-check deprecated options replaced by SPI_SPEED

Use next open E connector for Y2/Z2

Remove references to marlinfirmware.org

- Include aligned comment about new SDSUPPORT behavior

Fix handling of spaces in GCode

Development moved to https://github.com/thinkyhead/MarlinConfigurator

The domain is gone and doesn’t redirect, so for now show no URL on the boot screen.

Rename fpos_t to avoid libc conflict

Fix AUTOTEMP documentation in configs

Addresses issue #2715

Send the correct line number.
If no N was in the command - non't send an N.

Replace the "ok" in M280, M301, M304, M851 with output not including an "ok"
to avoid senting two "ok"s for a single g-code.

Doing the same for M105 would break the input filters of the hosts.
For M105 the other "ok" is omitted.

Rc bug fix

Rc bug fix

Instead of changing SDEXTRASLOW variable to a slower speed,  the new
SDULTRASLOW is used for rigidbot panel.

Rc bug fix

Rc bug fix

Fixing Rigidbot LCD Panel Support

Forgot Z2_MIN_PIN