db: split libdb_cxx into its own subpkg "libdb-cxx".

srcpkgs/db/libdb-cxx.template

@@ -0,0 +1,11 @@
+# Template file for 'libdb-cxx'.
+#
+revision=1
+short_desc="${short_desc} - C++ shared libraries"
+long_desc="${long_desc}
+
+ This package contains the C++ shared library for use in client programs."
+
+do_install() {
+	vmove "usr/lib/libdb_cxx*.so*" usr/lib
+}