input: rework how input sources are added

Until now, there were two functions to add input sources (stuff like
stdin input, slave mode, lirc, joystick). Unify them to a single
function (mp_input_add_fd()), and make sure the associated callbacks
always have a context parameter.

Change the lirc and joystick code such that they take store their state
in a context struct (probably worthless), and use the new mp_msg
replacements (the point of this refactoring).

Additionally, get rid of the ugly USE_FD0_CMD_SELECT etc. ifdeffery in
the terminal handling code.

input/lirc.h

@@ -19,12 +19,9 @@
 #ifndef MPLAYER_LIRC_H
 #define MPLAYER_LIRC_H
 
-int
-mp_input_lirc_init(void);
-
-int
-mp_input_lirc_read(int fd,char* dest, int s);
-
-int mp_input_lirc_close(int fd);
+struct input_ctx;
+struct mp_log;
+int mp_input_lirc_init(struct input_ctx *ictx, struct mp_log *log,
+                       char *lirc_configfile);
 
 #endif /* MPLAYER_LIRC_H */