Suppress unused parameter warnings #199

Job	Run time
osx (TOOLSET=clang CXXSTD=11,14,17,20 Job 5, boost, macos-13, clang++, 14.2.0, clang, 11,14,17,20)	14m 45s
posix (TOOLSET=gcc CXXSTD=11 Job 0, boost, ubuntu-latest, ubuntu:16.04, g++, gcc, 11)	5m 44s
posix (TOOLSET=gcc-5 CXXSTD=11,14,1z Job 1, boost, g++-5, ubuntu-latest, ubuntu:16.04, g++-5, gcc...	12m 26s
posix (TOOLSET=gcc-6 CXXSTD=11,14,1z Job 2, boost, g++-6, ubuntu-latest, ubuntu:16.04, g++-6, gcc...	12m 59s
posix (TOOLSET=gcc-7 CXXSTD=11,14,17 Job 3, boost, g++-7, ubuntu-latest, ubuntu:16.04, g++-7, gcc...	12m 19s
posix (TOOLSET=gcc-9 CXXSTD=11,14,17,20 Job 6, boost, g++-9, ubuntu-latest, ubuntu:16.04, g++-9, ...	13m 29s
posix (TOOLSET=clang CXXSTD=11,14,17,20 Job 4, boost, ubuntu-20.04, clang++, clang, 11,14,17,20)	14m 43s
	1h 26m 25s

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