Support partial tokens in salTTY
Output may well precede the SASL fragments, and a given buffer size may break up the token. This already occurred with lush DEBUG output before SASL,
DEBUG: sasl_stream := 0 at line 510
DEBUG: sasl_prefix := 0 at line 512
DEBUG: matchmay = 1 at line 515 after preliminarily comparing 4 to 4
DEBUG: matchmay = 1 at line 518 after comparing "sasl" to "sasl"
DEBUG: matchmay = 1 at line 526 after comparing 4 to 4
DEBUG: sasl_prefix := 1 at line 528
DEBUG: named==1 and sasl_prefix==1 at line 460
DEBUG: sasl_stream := 1 at line 465
DEBUG: Delivering remaining text after ASCII parsing in multtyflow_process_text() for type 1
DEBUG: Remainder = 05 1f 6e 6f 6e 63 65 3d 22 33 45 62 75 36 49 68 61 51 48 59 32 77 70 68 6c 53 6b 43 71 69 79 66 6f 79 74 42 58 47 42 30 7a 48 42 6d 36 31 45 37 45 72 77 51 3d 22 2c 72 65 61 -> #58
DEBUG: child_outflow_textcb event 1
DEBUG: Content in SASL stream, len=58, first=1, last=0
DEBUG: Parsing SASL = 05 1f 6e 6f 6e 63 65 3d 22 33 45 62 75 36 49 68 61 51 48 59 32 77 70 68 6c 53 6b 43 71 69 79 66 6f 79 74 42 58 47 42 30 7a 48 42 6d 36 31 45 37 45 72 77 51 3d 22 2c 72 65 61 -> #58
DEBUG: Entering SASL recursion on "nonce="3Ebu6IhaQHY2wphlSkCqiyfoytBXGB0zHBm61E7ErwQ=",rea" #58, going from flow 0x7ffc3b69e5d0 with text parser 0x5635601dd68b into stream 0x5635601e23a0 with text parser 0x5635601dc65f
DEBUG: Found start of S2C token
DEBUG: Delivering as a last-resort SASL parsing service
DEBUG: sasl_s2c_textcb event 110 text "nonce="3Ebu6IhaQHY2wphlSkCqiyfoytBXGB0zHBm61E7ErwQ=",rea"
DEBUG: SASL token is present
DEBUG: s2c = 6e 6f 6e 63 65 3d 22 33 45 62 75 36 49 68 61 51 48 59 32 77 70 68 6c 53 6b 43 71 69 79 66 6f 79 74 42 58 47 42 30 7a 48 42 6d 36 31 45 37 45 72 77 51 3d 22 2c 72 65 61 -> #56
##
## CRITICAL:
Assertion Failed on first && last at /home/root/pid2242117/multty.src/src/saltty.c:236 (Not Implemented Yet: Fragmented tokens)
This was after 960 bytes debugging, 6 bytes mulTTY switch to the "sasl" stream and only 56 bytes left for SASL itself, with a 1024 byte buffer. Extending that worked as a quickfix but is not the general solution.