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

Replaces g_ascii_strup() and allows building the Vorbis encoder
without GLib.

Replaces g_str_has_suffix().

Replaces g_strstrip().

Replaces GLib's g_str_has_prefix().

Overload the name.

Eliminate the fallback strndup() and strnlen() implementations.

Usually, when strndup() is not available, strndup() isn't either,
because both are POSIX 2008.

This patch also adds extern "C" { } wrapper around string_util.h
to allow its usage in C++ code

Remove GLib dependency from some headers.

Replace g_strchug() calls with a cheaper implementation.

It's not used anymore, its features have been moved to fd_util.c.

No CamelCase.  Use bool instead of int.  Make both arguments
mandatory.