Add back libvmod debug when flint'ing varnishd

My intention behind c021fbca was that
flexelint complains about symbols being defined multiple times.

Yet when we omit all vmods, we end up with lots of 759 (could be moved
from header to module).

So add back vmod_debug and have that refer more of the API.

bin/varnishd/flint.sh

@@ -19,4 +19,8 @@ FLOPS='
 	../../lib/libvarnish/*.c
 	../../lib/libvcc/flint.lnt
 	../../lib/libvcc/*.c
+	../../vmod/flint.lnt
+	../../vmod/vcc_debug_if.c
+	../../vmod/vmod_debug*.c
+	../../vmod/VSC_debug*.c
 ' ../../tools/flint_skel.sh

vmod/vmod_debug.c

@@ -505,8 +505,15 @@ event_warm(VRT_CTX, const struct vmod_priv *priv)
 {
 	struct priv_vcl *priv_vcl;
 	char buf[32];
+	const char *p[2];
+	struct strands msg[1];
 
-	VSL(SLT_Debug, 0, "%s: VCL_EVENT_WARM", VCL_Name(ctx->vcl));
+	// Using VSLs for coverage
+	msg->n = 2;
+	msg->p = p;
+	p[0] = VCL_Name(ctx->vcl);
+	p[1] = ": VCL_EVENT_WARM";
+	VSLs(SLT_Debug, 0, msg);
 
 	AN(ctx->msg);
 	if (cache_param->max_esi_depth == 42) {
@@ -805,6 +812,20 @@ xyzzy_sethdr(VRT_CTX, VCL_HEADER hs, VCL_STRANDS s)
 	}
 }
 
+// coverage
+static void
+mylog(struct vsl_log *vsl, enum VSL_tag_e tag,  const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	if (vsl != NULL)
+		VSLbv(vsl, tag, fmt, ap);
+	else
+		VSLv(tag, 0, fmt, ap);
+	va_end(ap);
+}
+
 VCL_DURATION
 xyzzy_priv_perf(VRT_CTX, VCL_INT size, VCL_INT rounds)
 {
@@ -838,7 +859,7 @@ xyzzy_priv_perf(VRT_CTX, VCL_INT size, VCL_INT rounds)
 
 	d = (t1 - t0) * 1e9 / ((double)size * (double)rounds);
 
-	VSLb(ctx->vsl, SLT_Debug,
+	mylog(ctx->vsl, SLT_Debug,
 	     "perf size %jd rounds %jd time %.1fns check %jd",
 	     (intmax_t)size, (intmax_t)rounds, d, (uintmax_t)check);
 
@@ -850,6 +871,7 @@ xyzzy_return_strands(VRT_CTX, VCL_STRANDS strand)
 {
 
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
+	VSLbs(ctx->vsl, SLT_Debug, strand);
 	return (strand);
 }