Revert "Removed unused math.h"

[dktapps]

This reverts commit 21bc33aae7759a730a6ec2b1de0523258e45a5cb.

#include "libmorton/include/morton.h"

int main() {
    return 0;
}

compiled with

clang++ test.cpp -I.

produces these errors:

clang++ test.cpp -I.
In file included from test.cpp:1:
In file included from ./libmorton/include/morton.h:9:
./libmorton/include/morton2D.h:120:42: error: use of undeclared identifier 'floor'
                unsigned int checkbits = (unsigned int)floor(sizeof(morton) * 4.0f);
                                                       ^
In file included from test.cpp:1:
In file included from ./libmorton/include/morton.h:10:
./libmorton/include/morton3D.h:70:21: error: use of undeclared identifier 'ceil'
                for (int i = (int)ceil((maxbit + 1) / 8.0f); i >= 0; --i) {
                                  ^
./libmorton/include/morton3D.h:128:54: error: use of undeclared identifier 'floor'
                unsigned int checkbits = static_cast<unsigned int>(floor((sizeof(morton) * 8.0f / 3.0f)));
                                                                   ^
./libmorton/include/morton3D.h:145:54: error: use of undeclared identifier 'floor'
                unsigned int checkbits = static_cast<unsigned int>(floor((sizeof(morton) * 8.0f / 3.0f)));
                                                                   ^
./libmorton/include/morton3D.h:256:54: error: use of undeclared identifier 'floor'
                unsigned int checkbits = static_cast<unsigned int>(floor((sizeof(morton) * 8.0f / 3.0f)));
                                                                   ^
./libmorton/include/morton3D.h:273:23: error: use of undeclared identifier 'floor'
                float defaultbits = floor((sizeof(morton) * 8.0f / 3.0f));
                                    ^
6 errors generated.

[Forceflow]

Ah poop, good catch. I only test with gcc