Replace CoinAbs by std::abs #36

Job	Run time
Run tests (ubuntu-20.04, true, ADD_CXXFLAGS=-fvisibility=hidden, sudo apt install -y -qq gfortran...	3m 57s
Run tests (ubuntu-20.04, false, ADD_CXXFLAGS=-fvisibility=hidden, sudo apt install -y -qq gfortra...	4m 0s
Run tests (ubuntu-22.04, true, ADD_CXXFLAGS=-fvisibility=hidden, sudo apt install -y -qq gfortran...	3m 52s
Run tests (ubuntu-22.04, false, ADD_CXXFLAGS=-fvisibility=hidden, sudo apt install -y -qq gfortra...	3m 56s
Run tests (macos-13, false, CC=clang OSX=13, brew install metis bash)	4m 34s
Run tests (macos-13, false, CC=gcc-13 CXX=g++-13 OSX=13 ADD_CXXFLAGS=-Wl,-ld_classic, brew instal...	5m 47s
Run tests (macos-14, false, CC=gcc-13 CXX=g++-13 OSX=14 ADD_CXXFLAGS=-Wl,-ld_classic, brew instal...	3m 33s
	29m 39s

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