stream_dvd: fix .ifo redirection

This was blatantly broken after stream->url was changed to talloc.
stream: remove inactive URL option fields

The URL option parser only accesses certain fields. Remove the fields
that are not accessed, and thus are completely unused and inaccessible.

Historically, these fields were supposed to be settable using an extra
list of options passed to open_stream(). Commit f518cf7 removed these
extra options. Apparently nothing ever actually used this facility.
crosscompile-mingw.txt: mingw-w64 now has modern OpenGL headers in trunk
crosscompile-mingw.txt: it's "MinGW" not "MingGW"
mpv.rc: update Windows icon

Based on the OSX bundle icon.
configure: fix vdpau test if vdpau is disabled/unavailable

The check for HAVE_AV_CODEC_NEW_VDPAU_API just determines whether the
new vdpau libavutil pixel format is available (which implies presence of
the new API). However, that pixel format (and the correspondig config
test define) is also used in generic code (compiled even without vdpau)
in fmt-conversion.c. Since the configure test didn't define the symbol
if vdpau was not available, it broke in this case.
vd_lavc: fix CONFIG_VDPAU check

CONFIG_VDPAU was just defined to 0, instead of undefined when vdpau was
unavailable. I blame the old mplayer code, which apparently can't have
consistent conventions.
vd_lavc: print warning if hardware decoding API is not available

At least currently, this case pretty much happens only in the case vdpau
is requested, but not compiled in.