osvrStartProcess implementation for non-windows systems

[JeroMiya]

This issue requires this pull request to be merged first:
#380

The osvrStartProcess function in osvrUtil has a commented out and untested implementation for non-windows systems. This needs to be tested and vetted, but should enable the server auto-start functionality for those systems.

[13r]

Tested it in osx and works ok.

Included a patch file.
0001-Issue-387.-Uncommented-and-tested-in-OSX.patch.zip