[sock] flush / handle lines during input handling when a telnet SB (r… #293

Job	Run time
build-maxos (3.8, --enable-python)	34s
build-maxos (3.8, --disable-widechar)	33s
build (3.8, --enable-lua)	20s
build-maxos (3.10, --enable-python)	27s
build (3.8, --enable-python)	18s
build-maxos (3.10, --disable-widechar)	28s
build (3.8, --disable-widechar)	22s
build_windows	0s
build-maxos (3.12, --enable-python)	20s
build (3.10, --enable-lua)	47s
build-maxos (3.12, --disable-widechar)	19s
build (3.10, --enable-python)	20s
build (3.10, --disable-widechar)	19s
build (3.12, --enable-lua)	40s
build (3.12, --enable-python)	24s
build (3.12, --disable-widechar)	37s
	6m 48s

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