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/peers.c b/src/peers.c
index 56256fa..bf22b93 100644
--- a/src/peers.c
+++ b/src/peers.c
@@ -1975,7 +1975,7 @@
 	int id = 0;
 
 	for (curpeer = peers->remote; curpeer; curpeer = curpeer->next) {
-		st = calloc(1,sizeof(struct shared_table));
+		st = calloc(1,sizeof(*st));
 		st->table = table;
 		st->next = curpeer->tables;
 		if (curpeer->tables)