Fix ruby 2.0 detection

lib/kross/configure.in.in

@@ -41,6 +41,12 @@ if test "x$compile_kross" = "xyes" ; then
           RUBY_CFLAGS=`$PKGCONFIG ruby-1.9 --cflags`
         fi
       fi
+      if test -z "$RUBY_VERSION"; then
+        RUBY_VERSION=`$PKGCONFIG ruby-2.0 --modversion 2>/dev/null`
+        if test -n "$RUBY_VERSION"; then
+          RUBY_CFLAGS=`$PKGCONFIG ruby-2.0 --cflags`
+        fi
+      fi
       if test -z "$RUBY_VERSION"; then
         # pkgconfig file does not exist but might be 1.9.1: RUBY_VERSION defined in ruby/version.h
         if test -n "$RUBY -r rbconfig -e 'printf("%s",RbConfig::CONFIG@<:@"rubyhdrdir"@:>@)'"; then