[flac-dev] test_streams dependencies

[lvqcl]

test_streams currently depends on grabbag and (on Windows) on win_utf8_io libs.
It depends on win_utf8_io only because it uses flac_fopen() function.

It will become to depend on libFLAC when all file functions will be moved
 from win_utf8_io to libFLAC. Not a big problem, but it is possible to avoid
this dependency by replacing flac_fopen() with fopen().

test_streams doesn't open/create files with unicode filenames, so it won't
affect its functionality.

So, what's better:
a) replace all flac_fopen() calls inside test_streams/main.c with fopen()
b) leave it as is, so that on Windows build of test_streams will depend on libFLAC