patch 9.0.0977: it is not easy to see what client-server commands are doing

Problem:    It is not easy to see what client-server commands are doing.
Solution:   Add channel log messages if ch_log() is available.  Move the
            channel logging and make it available with the +eval feature.
diff --git a/src/regexp_bt.c b/src/regexp_bt.c
index 42b6ac2..d2acbc2 100644
--- a/src/regexp_bt.c
+++ b/src/regexp_bt.c
@@ -3163,7 +3163,7 @@
     {
 	if (timed_out != NULL)
 	{
-# ifdef FEAT_JOB_CHANNEL
+# ifdef FEAT_EVAL
 	    if (!*timed_out)
 		ch_log(NULL, "BT regexp timed out");
 # endif