Added system_time_ticks to C interface

lispBM/c_libs/vesc_c_if.h

@@ -611,6 +611,10 @@ typedef struct {
 	// Unblock unboxed
 	bool (*lbm_unblock_ctx_unboxed)(lbm_cid cid, lbm_value unboxed);
 
+	// Time since boot in system ticks. Resolution: 100 uS.
+	// Use ts_to_age_s to get the age of a timestamp in
+	// seconds. ts_to_age_s should hanlde overflows.
+	systime_t (*system_time_ticks)(void);
 } vesc_c_if;
 
 typedef struct {

lispBM/lispif_c_lib.c

@@ -932,6 +932,9 @@ lbm_value ext_load_native_lib(lbm_value *args, lbm_uint argn) {
 		// Unblock unboxed
 		cif.cif.lbm_unblock_ctx_unboxed = lbm_unblock_ctx_unboxed;
 
+		// System time
+		cif.cif.system_time_ticks = chVTGetSystemTimeX;
+
 		lib_init_done = true;
 	}