CrystalHD: support for opening the BCM dll under Win32

On a normal Win32 released build, we aren't going to ship the BCM dll
or ask our users to install the good version of the dll at the right
place and recompute the plugins cache...
Therefore, we need to open the dll and resolve the symbols.

configure.ac

@@ -2462,12 +2462,16 @@ if test "${enable_crystalhd}" == "yes"; then
       VLC_ADD_PLUGIN([crystalhd])
       VLC_ADD_LIBS([crystalhd], [-lcrystalhd])
     ],[
-        AC_CHECK_HEADERS(libcrystalhd/bc_drv_if.h, [
+      if test "${SYS}" = "mingw32" ; then
+        AC_CHECK_HEADERS(libcrystalhd/bc_dts_defs.h, [
           VLC_ADD_PLUGIN([crystalhd])
+          AC_CHECK_HEADERS(libcrystalhd/bc_drv_if.h, [
             VLC_ADD_LIBS([crystalhd], [-lbcmDIL])
+            ])
         ],[
           AC_MSG_ERROR("Could not find CrystalHD development headers")
         ])
+      fi
     ])
 fi