configure: use c++98 for c++ files

Use c++98 standard instead of c++11.

Signed-off-by: Rick Kern <kernrj@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

configure

@@ -4529,7 +4529,7 @@ fi
 
 add_cppflags -D_ISOC99_SOURCE
 add_cxxflags -D__STDC_CONSTANT_MACROS
-add_cxxflags -std=c++11
+add_cxxflags -std=c++98
 check_cflags -std=c99
 check_cc -D_FILE_OFFSET_BITS=64 <<EOF && add_cppflags -D_FILE_OFFSET_BITS=64
 #include <stdlib.h>