[ci skip] Migrate libxmlrpc README to Markdown

Author: petk

ext/xmlrpc/libxmlrpc/README

@@ -0,0 +1,21 @@
+# libxmlrpc
+
+This is a fork of the [xmlrpc-epi library](http://xmlrpc-epi.sourceforge.net/)
+written by Dan Libby.
+
+## Original coding conventions
+
+Organization of this directory is moving towards this approach:
+
+* `<module>.h`         -- public API and data types
+* `<module>_private.h` -- protected API and data types
+* `<module>.c`         -- implementation and private API / types
+
+The rules are:
+
+* `.c` files may include `*_private.h`.
+* `.h` files may not include `*_private.h`
+
+This allows us to have a nicely encapsulated C api with opaque data types and
+private functions that are nonetheless shared between source files without
+redundant extern declarations..