The "pure" and "const" attributes are not so well-defined, and a
recent clang version implements an optimization which pushes the
definition's boundary beyond what I believed it was.  clang now
assumes that functions declared "pure" cannot throw exceptions, even
if they lack the "noexcept" specification.

When compiled with this new clang version, MPD will crash randomly if
an exception happens to get thrown by such as "pure" function
(https://github.com/MusicPlayerDaemon/MPD/issues/41).

This commit removes all such misplaced "pure" and "const" attributes,
closing #41.

The old check

 unsigned(value) > std::numeric_limits<unsigned>::max()

.. cannot ever fail.

Wrapper for protocol/ArgParser.cxx.

Using unsigned(-1) renders undefined behavior.

Casting std::numeric_limits<unsigned>::max() to "long" leads to an
overflow if sizeof(unsigned)==sizeof(long), and the result will be -1.

This happens on some 32 bit architectures, for example ARM and WIN32.

Workaround: use std::numeric_limits<int>::max(), which is the largest
signed integer.  Since sizeof(long)>=sizeof(int), this will never
overflow.

Fixes Mantis ticket 0004080.

Copy the according file from another project (i.e. XCSoar).  This will
allow copying more code more easily.

Replaces GLib's GError.

If END is omitted, mpd should use the highest possible value instead of raising an error.
This partially reverts 52e9cab1

Remove GLib dependency from some headers.