adding libdv m4 check

Original commit message from CVS:
adding libdv m4 check

m4/libdv.m4

@@ -0,0 +1,108 @@
+# Configure paths for libdv
+# copied from vorbis.m4 by Thomas
+# checks for libdv 0.9.5 since that added an extra argument to _init
+# Shamelessly stolen from Owen Taylor and Manish Singh
+
+dnl AM_PATH_LIBDV([ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND]])
+dnl Test for liblibdv, and define LIBDV_CFLAGS and LIBDV_LIBS
+dnl
+AC_DEFUN(AM_PATH_LIBDV,
+[dnl 
+dnl Get the cflags and libraries
+
+AC_ARG_WITH(libdv,[  --with-libdv=PFX   Prefix where libdv is installed (optional)], libdv_prefix="$withval", libdv_prefix="")
+AC_ARG_WITH(libdv-libraries,[  --with-libdv-libraries=DIR   Directory where libdv library is installed (optional)], libdv_libraries="$withval", libdv_libraries="")
+AC_ARG_WITH(libdv-includes,[  --with-libdv-includes=DIR   Directory where libdv header files are installed (optional)], libdv_includes="$withval", libdv_includes="")
+AC_ARG_ENABLE(libdvtest, [  --disable-libdvtest       Do not try to compile and run a test libdv program],, enable_libdvtest=yes)
+
+  if test "x$libdv_libraries" != "x" ; then
+    LIBDV_LIBS="-L$libdv_libraries"
+  elif test "x$libdv_prefix" != "x" ; then
+    LIBDV_LIBS="-L$libdv_prefix/lib"
+  elif test "x$prefix" != "xNONE"; then
+    LIBDV_LIBS="-L$prefix/lib"
+  fi
+
+  LIBDV_LIBS="$LIBDV_LIBS -ldv"
+
+  if test "x$libdv_includes" != "x" ; then
+    LIBDV_CFLAGS="-I$libdv_includes"
+  elif test "x$libdv_prefix" != "x" ; then
+    LIBDV_CFLAGS="-I$libdv_prefix/include"
+  elif test "x$prefix" != "xNONE"; then
+    LIBDV_CFLAGS="-I$prefix/include"
+  fi
+
+
+  AC_MSG_CHECKING(for libdv)
+  no_libdv=""
+
+
+  if test "x$enable_libdvtest" = "xyes" ; then
+    ac_save_CFLAGS="$CFLAGS"
+    ac_save_LIBS="$LIBS"
+    CFLAGS="$CFLAGS $LIBDV_CFLAGS"
+    LIBS="$LIBS $LIBDV_LIBS"
+dnl
+dnl Now check if the installed libdv is sufficiently new.
+dnl
+      dnl rm -f conf.libdvtest
+      AC_TRY_RUN([
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <libdv/dv.h>
+
+int main ()
+{
+  dv_decoder_new (0, 0, 0);
+  return 0;
+}
+
+],, no_libdv=yes,[echo $ac_n "cross compiling; assumed OK... $ac_c"])
+       CFLAGS="$ac_save_CFLAGS"
+       LIBS="$ac_save_LIBS"
+  fi
+
+  if test "x$no_libdv" = "x" ; then
+     AC_MSG_RESULT(yes)
+     ifelse([$1], , :, [$1])     
+  else
+     AC_MSG_RESULT(no)
+     if test -f conf.libdvtest ; then
+       :
+     else
+       echo "*** Could not run libdv test program, checking why..."
+       CFLAGS="$CFLAGS $LIBDV_CFLAGS"
+       LIBS="$LIBS $LIBDV_LIBS"
+       AC_TRY_LINK([
+#include <stdio.h>
+#include <libdv/dv.h>
+],     [ return 0; ],
+       [ echo "*** The test program compiled, but did not run. This usually means"
+       echo "*** that the run-time linker is not finding libdv or finding the wrong"
+       echo "*** version of libdv. If it is not finding libdv, you'll need to set your"
+       echo "*** LD_LIBRARY_PATH environment variable, or edit /etc/ld.so.conf to point"
+       echo "*** to the installed location  Also, make sure you have run ldconfig if that"
+       echo "*** is required on your system"
+       echo "***"
+       echo "*** If you have an old version installed, it is best to remove it, although"
+       echo "*** you may also be able to get things to work by modifying LD_LIBRARY_PATH"],
+       [ echo "*** The test program failed to compile or link. See the file config.log for the"
+       echo "*** exact error that occured. This usually means libdv was incorrectly installed"
+       echo "*** or that you have moved libdv since it was installed." ])
+       CFLAGS="$ac_save_CFLAGS"
+       LIBS="$ac_save_LIBS"
+     fi
+     LIBDV_CFLAGS=""
+     LIBDV_LIBS=""
+     LIBDVFILE_LIBS=""
+     LIBDVENC_LIBS=""
+     ifelse([$2], , :, [$2])
+  fi
+  AC_SUBST(LIBDV_CFLAGS)
+  AC_SUBST(LIBDV_LIBS)
+  AC_SUBST(LIBDVFILE_LIBS)
+  AC_SUBST(LIBDVENC_LIBS)
+  dnl rm -f conf.libdvtest
+])