Replace BaseLib::swap with std::swap.

BaseLib/quicksort.h

BaseLib/swap.h

FileIO/MeshIO/GMSHInterface.cpp

GeoLib/Polygon.cpp

GeoLib/Polyline.cpp

MathLib/AnalyticalGeometry.cpp

MathLib/EarClippingTriangulation.cpp

.../InterpolationAlgorithms/PiecewiseLinearInterpolation.cpp

MathLib/LinAlg/Solvers/GaussAlgorithm.cpp

MathLib/LinAlg/Sparse/CRSMatrix.h

MathLib/LinAlg/Sparse/NestedDissectionPermutation/AdjMat.cpp

...Sparse/NestedDissectionPermutation/CRSMatrixReordered.cpp

...Lib/LinAlg/Sparse/NestedDissectionPermutation/Cluster.cpp

...b/LinAlg/Sparse/NestedDissectionPermutation/Separator.cpp

Tests/BaseLib/TestSwap.cpp