CLEANUP: uniformize last argument of malloc/calloc

Instead of repeating the type of the LHS argument (sizeof(struct ...))
in calls to malloc/calloc, we directly use the pointer
name (sizeof(*...)). The following Coccinelle patch was used:

@@
type T;
T *x;
@@

  x = malloc(
- sizeof(T)
+ sizeof(*x)
  )

@@
type T;
T *x;
@@

  x = calloc(1,
- sizeof(T)
+ sizeof(*x)
  )

When the LHS is not just a variable name, no change is made. Moreover,
the following patch was used to ensure that "1" is consistently used as
a first argument of calloc, not the last one:

@@
@@

  calloc(
+ 1,
  ...
- ,1
  )
diff --git a/src/dns.c b/src/dns.c
index 14c3b6b..1ce786d 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -909,7 +909,7 @@
 		curr_resolvers->t = t;
 
 		list_for_each_entry(curnameserver, &curr_resolvers->nameserver_list, list) {
-			if ((dgram = calloc(1, sizeof(struct dgram_conn))) == NULL) {
+			if ((dgram = calloc(1, sizeof(*dgram))) == NULL) {
 				Alert("Starting [%s/%s] nameserver: out of memory.\n", curr_resolvers->id,
 						curnameserver->id);
 				return 0;