build: fix gcc7 implicit fallthrough warnings

Mark intended fallthroughs with /* FALLTHROUGH */ so that gcc will know
it's expected and won't warn on [-Wimplicit-fallthrough=].

Closes https://github.com/curl/curl/pull/1297

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/ftp.c b/lib/ftp.c
index 867c97994..a1546a135 100644
--- a/lib/ftp.c
+++ b/lib/ftp.c
@@ -3214,6 +3214,7 @@ static CURLcode ftp_done(struct connectdata *conn, CURLcode status,
 
     /* until we cope better with prematurely ended requests, let them
      * fallback as if in complete failure */
+    /* FALLTHROUGH */
   default:       /* by default, an error means the control connection is
                     wedged and should not be used anymore */
     ftpc->ctl_valid = FALSE;