Input clock reference: bump maximum gap to 60s

Some APE files can have a single packet duration of up to 30s
Is there even a hard limit in this format, or can packets be longer?

Previous gap limit was an arbitrary 22s, written in a way reminiscent of
the MPEG 90kHz clock, which does not make sense anymore since reference clock
in all our demuxers use our own 1MHz clock.

Also explicitely use CLOCK_FREQ

src/input/clock.c

@@ -80,7 +80,7 @@
  *****************************************************************************/
 
 /* Maximum gap allowed between two CRs. */
-#define CR_MAX_GAP (INT64_C(2000000)*100/9)
+#define CR_MAX_GAP (60 * CLOCK_FREQ)
 
 /* Latency introduced on DVDs with CR == 0 on chapter change - this is from
  * my dice --Meuuh */