MacOs compilation failure

[blaind]

The library possibly fails to compile on MacOS:

warning: ttf2mesh/ttf2mesh.c:54:10: fatal error: 'malloc.h' file not found
warning: #include <malloc.h>
warning:          ^~~~~~~~~~
warning: 1 error generated.

There's a related stackoverflow question about malloc.h at https://stackoverflow.com/a/56463133/499839

One option would be to transpile ttfmesh.c into rust by https://c2rust.com/. That could also fix #11