Add HAMLIB_CACHE_ALWAYS

Enable for rig_get_freq
https://github.com/Hamlib/Hamlib/issues/880

include/hamlib/rig.h

@@ -2199,6 +2199,8 @@ typedef hamlib_port_t port_t;
 #define HAMLIB_ELAPSED_SET 1
 #define HAMLIB_ELAPSED_INVALIDATE 2
 
+#define HAMLIB_CACHE_ALWAYS -1 /*< value to set cache timeout to always use cache */
+
 typedef enum {
     HAMLIB_CACHE_ALL, // to set all cache timeouts at once
     HAMLIB_CACHE_VFO,

src/rig.c

@@ -2177,7 +2177,7 @@ int HAMLIB_API rig_get_freq(RIG *rig, vfo_t vfo, freq_t *freq)
 
     cache_show(rig, __func__, __LINE__);
 
-    if (*freq != 0 && cache_ms_freq < rig->state.cache.timeout_ms)
+    if (*freq != 0 && (cache_ms_freq < rig->state.cache.timeout_ms || rig->state.cache.timeout_ms == HAMLIB_CACHE_ALWAYS))
     {
         rig_debug(RIG_DEBUG_TRACE, "%s: %s cache hit age=%dms, freq=%.0f\n", __func__,
                   rig_strvfo(vfo), cache_ms_freq, *freq);