package/libb64: new package

package/libb64: new package

This patch adds libb64, a library of ANSI C routines for fast
encoding/decoding data into and from a base64-encoded format.

The package contains a static library, headers, and an executable.
The latter, however, requires C++ and offers no advantages over busybox
or coreutils base64, so it is not installed. Therefore, nothing is
installed to target.

Signed-off-by: Angelo Compagnucci <angelo.compagnucci@gmail.com>
[Arnout:
- properly wrap Config.in
- move from Crypto to Other menu
- don't install to target
- don't make headers executable
- don't add -D to install with multiple source files
- extend commit log]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>