Remove dead preferences window code.

Conflicts:
	src/audacious/ui_preferences.c
Remove old string pool debug code.
Remove str_unref() wrappers.
Use (const char *) for string literals.
Fix regression in 7aaf07d1e2a7 that loaded non-UTF-8 text into the playlist.
Fix str_nget() reading past len bytes.
Tuple compiler: change (char *) to (const char *) where appropriate.
Fix memory leak.
Fix memory leak.

Conflicts:
	src/libaudcore/vfs.c
Add missing prototype for vfs_fputs().
man: Capitalize 'audacious'.
Remove a completely useless function.
Fix infinite loop upon encountering a recursive symbolic link.
Call plugin_misc_cleanup() correctly when switching interface or output plugins.
Work around GtkTreeView's annoying set_cell_data() warning.
Fix unterminated string.