Use uri_has_scheme to find out if the href in Webdav responses is absolute
to use the matching base path extraction.
Signed-off-by: Vincent Petry <PVince81@yahoo.fr>

The ones in std have overloads for const char/char.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

Reduce overhead by not duplicating the string.

Required according to RFC 3986:

> An implementation should accept uppercase letters as equivalent to
> lowercase in scheme names

Closes #330

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

New in clang 3.6.

A file called ".jpg" is not a JPEG file with an empty name; it is
merely a hidden file.

Replaces g_uri_parse_scheme().

Micro-optimization.

g_basename() is deprecated in GLib 2.32.  Instead, verify that the
suffix does not have a backslash, to catch Windows path names.

This buggy implementation failed to allow "..." sequences, because the
dot count was always zero.  The usefulness of allowing "..." (or more
dots) is debatable, but since it's a valid file name, we allow it.

Dots at the beginning of an URI segment are ok, as long as the special
names "." and ".." are not used.