Don't remove AC_PROG_CPP our headerfile and library checking macros depend on...

Don't remove AC_PROG_CPP our headerfile and library checking macros depend on it. Unbreak configure.ac

configure.ac

@@ -41,6 +41,7 @@ AC_PROG_CC_C99
 AC_USE_SYSTEM_EXTENSIONS
 AM_PROG_CC_C_O
 AC_PROG_CXX
+AC_PROG_CPP
 AC_PROG_OBJC
 _AM_DEPENDENCIES([OBJC])
 AC_PROG_EGREP
@@ -114,6 +115,9 @@ dnl kludge because only the debian package provides a ffmpeg-config
     if test -z $with_cyberlink_tree; then
        with_cyberlink_tree=${topdir}/extras/contrib/src/clinkcc
     fi
+    if test -z $with_libmpeg2_tree; then
+	with_libmpeg2_tree=${topdir}/extras/contrib/src/mpeg2dec
+    fi
 
     if test ".`uname -s`" = ".Darwin"; then
       export LD_LIBRARY_PATH=${topdir}/extras/contrib/lib:$LD_LIBRARY_PATH