Split the matrix tests into two files to speed up compilation of the regression tests.

--HG--
rename : dlib/test/matrix.cpp => dlib/test/matrix2.cpp
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402716

dlib/test/CMakeLists.txt

@@ -42,6 +42,7 @@ set (tests
    lz77_buffer.cpp
    map.cpp
    matrix.cpp
+   matrix2.cpp
    md5.cpp
    member_function_pointer.cpp
    metaprogramming.cpp