The environment for building the DLL needs to be quite different from
the environment for building the programs, in order to get
the dllexport/dllimport attribute done currectly. I don't know how MinGW
managed to build the programs, but MS linker refuses to link symbols with
mismatching attributes.
This is a substantial reorganization, This particular commit enables:
- building the progs for unices platforms
- glew is now built as a shared library (it is the default, and it is
inconvenient and pointless to shift away from that default)
- all progs get built by default
