Standards.PKCS.Signature: Added class Signed.

sign() now returns a Signed.
Standards.ASN1: Fix UTC type to actually use UTC

Previously it would encode/decode as local time.

Also, adjusted test cases accordingly.
GTK2: Test for existence of glib schar functions
Image.SVG: Use rsvg_init if librsvg is older than 2.36
CritBit: Support 0.0.0.0/0 on 32 bit systems
Fixed a crash reported by Martin Bähr.
Inotify: Include file_machine.h before file.h.

_Stdio/file.h has dependencies on configure checks.
Make sure that they are valid.
Stdio: Some code cleanup for get_dir().
Stdio: Added File()->get_dir().

Added function for getting the directory contents relative to an open
file.