The ValKind::operator<< uses ostream, but the include was missing. os… #1534

Job	Run time
doc	7s
test (ubuntu-latest, Release, -DCMAKE_CXX_COMPILER=clang++)	31s
test (ubuntu-latest, Debug, -DCMAKE_CXX_COMPILER=clang++)	26s
test (ubuntu-latest, Debug, -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_CXX_FLAGS="-fsanitize=address -f...	29s
test (ubuntu-latest, Debug, -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_CXX_FLAGS="-fsanitize=undefined ...	28s
test (ubuntu-latest, Release, true, -DCMAKE_CXX_COMPILER=g++-10)	46s
test (ubuntu-latest, Debug, true, -DCMAKE_CXX_COMPILER=g++-10)	33s
test (macos-latest, Release)	21s
test (macos-latest, Debug)	21s
test (windows-latest, Debug, -T ClangCL)	2m 2s
test (windows-latest, Release, -T ClangCL)	2m 34s
test (windows-latest, Debug)	1m 53s
test (windows-latest, Release)	1m 58s
	12m 29s

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