Add LZSS encoding/decoding for MKRNB 1500 SBU

[giulcioffi]

This PR provides the possibility to store a .lzss compressed binary in the SARA-R410M module and decode it back to a binary during the reboot by the SBU. The example SBU_LoadLZSS.ino allows to test it.
The lzss library is provided under /libraries/SBU/extras/SBUBoot with a symlink to /libraries/SBU/examples/SBU_LoadLZSS.
First of all, the function void lzss_init(uint32_t const sketch_start, bool LZSStoBIN) must be called. There are 2 possibilities:

• lzss_init(0, false) : we want to perform a LZSS encoding (.H -> .LZSS);
• lzss_init(SKETCH_START, true) : we want to perform a LZSS decoding (.LZSS -> .H), with SKETCH_START the address of the flash were the decoded file must be written.
  The function int lzss_encode(const char buf_in[], uint32_t size) reads the incoming buffer (from BINARY.H), performs the lzss encoding by chunks of 512 bytes and writes the obtained characters into the Sara modem in a file called "UPDATE.BIN.LZSS".
  On the other hand, the function void lzss_decode() reads the encoded "UPDATE.BIN.LZSS", decodes it back to a binary stream and writes it into the flash.

[aentinger]

LGTM 👍 Successfully tested with MKR NB 1500 👍 Thank you @giulcioffi 🚀