test

Fix buffer overflow at ungetc #332

Job	Run time
build (3.1 / windows-latest)	17s
build (3.0 / macos-latest)	17s
build (3.0 / ubuntu-latest)	16s
build (mswin / windows-latest)	17s
build (2.7 / macos-latest)	16s
build (3.1 / macos-latest)	23s
build (3.1 / ubuntu-latest)	15s
build (head / ubuntu-latest)	13s
build (2.7 / windows-latest)	17s
build (truffleruby-head / ubuntu-latest)	14s
build (3.0 / windows-latest)	18s
build (2.7 / ubuntu-latest)	32s
build (truffleruby-head / macos-latest)	16s
build (mingw / windows-latest)	15s
build (head / macos-latest)	13s
	4m 19s

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