SerialStreamer: Print signed decimal numbers correctly. (#92) #419

Job	Run time
ubuntu-20.04, gcc 7-2017-q4, cmake 3.6.0	1m 8s
ubuntu-20.04, gcc 7-2017-q4, cmake latest	1m 3s
ubuntu-20.04, gcc latest, cmake 3.6.0	1m 16s
ubuntu-20.04, gcc latest, cmake latest	1m 25s
macos-12, gcc 7-2017-q4, cmake 3.6.0	1m 13s
macos-12, gcc 7-2017-q4, cmake latest	1m 44s
macos-12, gcc latest, cmake 3.6.0	1m 54s
macos-12, gcc latest, cmake latest	2m 6s
windows-2019, gcc 7-2017-q4, cmake 3.6.0	1m 58s
windows-2019, gcc 7-2017-q4, cmake latest	2m 27s
windows-2019, gcc latest, cmake 3.6.0	2m 14s
windows-2019, gcc latest, cmake latest	2m 28s
	20m 56s

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