Upgrade LEN_MAX up to 512 for all combinators by default

[AkechiShiro]

• Added a gcc argument in the Makefile CFLAGS for defining a variable LEN_MAX that will be set by default at 512.
• if more is needed, running make LEN_MAX=<max_value_needed> will compile the combinators binaries with the proper changes.

I needed to combine wordlist that had long long strings, hence why this PR.

Was also assisted by @3ldidi94