We usually did this, but sometimes they were named after what they did,
rather than what they cleaned up.
There are still a few exceptions:
1. I didn't bother creating destroy_xxx wrappers for htable routines
which already existed.
2. Sometimes destructors really are used for side-effects (eg. to simply
mark that something was freed): these are clearer with boutique names.
3. Generally destructors are static, but they don't need to be: in some
cases we attach a destructor then remove it later, or only attach
to *some* cases. These are best with qualifiers in the destroy_<type>
name.
Suggested-by: @ZmnSCPxj
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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