MINOR: xprt/mux: export all *_io_cb functions so that "show fd" resolves them

In FD dumps it's often very important to figure what upper layer function
is going to be called. Let's export the few I/O callbacks that appear as
tasklet functions so that "show fd" can resolve them instead of printing
a pointer relative to main. For example:

   1028 : st=0x21(R:rA W:Ra) ev=0x01(heopI) [lc] tmask=0x2 umask=0x2 owner=0x7f00b889b200 iocb=0x65b638(sock_conn_iocb) back=0 cflg=0x00001300 fe=recv mux=H2 ctx=0x7f00c8824de0 h2c.st0=FRH .err=0 .maxid=795 .lastid=-1 .flg=0x0000 .nbst=0 .nbcs=0 .fctl_cnt=0 .send_cnt=0 .tree_cnt=0 .orph_cnt=0 .sub=1 .dsi=795 .dbuf=0@(nil)+0/0 .msi=-1 .mbuf=[1..1|32],h=[0@(nil)+0/0],t=[0@(nil)+0/0] xprt=SSL xprt_ctx=0x7f00c86d0750 xctx.st=0 .xprt=RAW .wait.ev=1 .subs=0x7f00c88252e0(ev=1 tl=0x7f00a07d1aa0 tl.calls=1047 tl.ctx=0x7f00c8824de0 tl.fct=h2_io_cb) .sent_early=0 .early_in=0

(cherry picked from commit 691d503896f2dc4944782cfe989fc8b44d66a6c0)
[wt: context adjustments; dropped quic]
Signed-off-by: Willy Tarreau <w@1wt.eu>
diff --git a/src/mux_fcgi.c b/src/mux_fcgi.c
index 46c77cb..afc6423 100644
--- a/src/mux_fcgi.c
+++ b/src/mux_fcgi.c
@@ -353,7 +353,8 @@
 
 static struct task *fcgi_timeout_task(struct task *t, void *context, unsigned short state);
 static int fcgi_process(struct fcgi_conn *fconn);
-static struct task *fcgi_io_cb(struct task *t, void *ctx, unsigned short state);
+/* fcgi_io_cb is exported to see it resolved in "show fd" */
+struct task *fcgi_io_cb(struct task *t, void *ctx, unsigned short state);
 static inline struct fcgi_strm *fcgi_conn_st_by_id(struct fcgi_conn *fconn, int id);
 static struct task *fcgi_deferred_shut(struct task *t, void *ctx, unsigned short state);
 static struct fcgi_strm *fcgi_conn_stream_new(struct fcgi_conn *fconn, struct conn_stream *cs, struct session *sess);
@@ -2926,7 +2927,7 @@
 }
 
 /* this is the tasklet referenced in fconn->wait_event.tasklet */
-static struct task *fcgi_io_cb(struct task *t, void *ctx, unsigned short status)
+struct task *fcgi_io_cb(struct task *t, void *ctx, unsigned short status)
 {
 	struct connection *conn;
 	struct fcgi_conn *fconn;