[master] 9a42663cd param: Clarify the poolparam::max_age type

[Dridi Boukelmoune]

commit 9a42663cd7dd942a8e98b8106d0db028f62802df
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Tue Jan 11 07:34:12 2022 +0100

    param: Clarify the poolparam::max_age type
    
    Refs #3766

diff --git a/bin/varnishd/common/common_param.h b/bin/varnishd/common/common_param.h
index 785e20579..fb8eb4775 100644
--- a/bin/varnishd/common/common_param.h
+++ b/bin/varnishd/common/common_param.h
@@ -68,7 +68,7 @@ COM_FEATURE(const volatile uint8_t *p, enum feature_bits x)
 struct poolparam {
 	unsigned		min_pool;
 	unsigned		max_pool;
-	double			max_age;
+	vtim_dur		max_age;
 };