Typo in SparseMatrix.hpp - unorderd_map

[christopheredsall]

Attempting to build with a modern GCC I get

/usr/bin/g++ -c -DHPCG_NO_MPI -I./src -I./src/GCC_OMP  -O3 -ffast-math -ftree-vectorize -ftree-vectorizer-verbose=0 -fopenmp -I../src ../src/main.cpp -o src/main.o
In file included from ../src/GenerateProblem.hpp:17:0,
                 from ../src/main.cpp:42:
../src/SparseMatrix.hpp:36:31: error: ‘unorderd_map’ in namespace ‘std’ does not name a template type
 using GlobalToLocalMap = std::unorderd_map< global_int_t, local_int_t >;
                               ^~~~~~~~~~~~

Spelling it unordered_map allows the build to complete

[christopheredsall]

I should have cheked the issues more thoroughly - this duplicates part of #43