Replace CoinAbs by std::abs #259

Job	Run time
Run tests (ubuntu-20.04, true, ADD_CXXFLAGS=-fvisibility=hidden, sudo apt install -y -qq gfortran...	1m 23s
Run tests (ubuntu-20.04, false, ADD_CXXFLAGS=-fvisibility=hidden, sudo apt install -y -qq gfortra...	1m 19s
Run tests (ubuntu-22.04, true, ADD_CXXFLAGS=-fvisibility=hidden, sudo apt install -y -qq gfortran...	1m 26s
Run tests (ubuntu-22.04, false, ADD_CXXFLAGS=-fvisibility=hidden, sudo apt install -y -qq gfortra...	1m 31s
Run tests (macos-13, false, CC=clang OSX=13, brew install metis bash)	2m 20s
Run tests (macos-13, false, CC=gcc-13 CXX=g++-13 OSX=13 ADD_CXXFLAGS=-Wl,-ld_classic, brew instal...	2m 45s
Run tests (macos-14, false, CC=gcc-13 CXX=g++-13 OSX=14 ADD_CXXFLAGS=-Wl,-ld_classic, brew instal...	1m 32s
	12m 16s

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