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/os_unix.c b/src/os_unix.c
index c43d9c1..79d7f17 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -4747,7 +4747,7 @@
 	    reset_signals();		// handle signals normally
 	    UNBLOCK_SIGNALS(&curset);
 
-# ifdef FEAT_JOB_CHANNEL
+# ifdef FEAT_EVAL
 	    if (ch_log_active())
 	    {
 		ch_log(NULL, "closing channel log in the child process");
@@ -5465,7 +5465,7 @@
     char_u	*cmd,
     int		options)	// SHELL_*, see vim.h
 {
-#ifdef FEAT_JOB_CHANNEL
+#ifdef FEAT_EVAL
     ch_log(NULL, "executing shell command: %s", cmd);
 #endif
 #if defined(FEAT_GUI) && defined(FEAT_TERMINAL)
@@ -5597,7 +5597,7 @@
 	reset_signals();		// handle signals normally
 	UNBLOCK_SIGNALS(&curset);
 
-# ifdef FEAT_JOB_CHANNEL
+# ifdef FEAT_EVAL
 	if (ch_log_active())
 	    // close the log file in the child
 	    ch_logfile((char_u *)"", (char_u *)"");
@@ -8324,7 +8324,7 @@
 	timer_created = TRUE;
     }
 
-# ifdef FEAT_JOB_CHANNEL
+# ifdef FEAT_EVAL
     ch_log(NULL, "setting timeout timer to %d sec %ld nsec",
 	       (int)interval.it_value.tv_sec, (long)interval.it_value.tv_nsec);
 # endif