tree-wide: Convert compare_func's to use CMP() macro wherever possible.

Looked for definitions of functions using the *_compare_func() suffix.

Tested:
- Unit tests passed (ninja -C build/ test)
- Installed this build and booted with it.

src/basic/hash-funcs.c

@@ -71,7 +71,7 @@ void trivial_hash_func(const void *p, struct siphash *state) {
 }
 
 int trivial_compare_func(const void *a, const void *b) {
-        return a < b ? -1 : (a > b ? 1 : 0);
+        return CMP(a, b);
 }
 
 const struct hash_ops trivial_hash_ops = {
@@ -87,7 +87,7 @@ int uint64_compare_func(const void *_a, const void *_b) {
         uint64_t a, b;
         a = *(const uint64_t*) _a;
         b = *(const uint64_t*) _b;
-        return a < b ? -1 : (a > b ? 1 : 0);
+        return CMP(a, b);
 }
 
 const struct hash_ops uint64_hash_ops = {
@@ -104,7 +104,7 @@ int devt_compare_func(const void *_a, const void *_b) {
         dev_t a, b;
         a = *(const dev_t*) _a;
         b = *(const dev_t*) _b;
-        return a < b ? -1 : (a > b ? 1 : 0);
+        return CMP(a, b);
 }
 
 const struct hash_ops devt_hash_ops = {

src/basic/in-addr-util.c

@@ -581,9 +581,11 @@ void in_addr_data_hash_func(const void *p, struct siphash *state) {
 
 int in_addr_data_compare_func(const void *a, const void *b) {
         const struct in_addr_data *x = a, *y = b;
+        int r;
 
-        if (x->family != y->family)
-                return x->family - y->family;
+        r = CMP(x->family, y->family);
+        if (r != 0)
+                return r;
 
         return memcmp(&x->address, &y->address, FAMILY_ADDRESS_SIZE(x->family));
 }

src/basic/process-util.c

@@ -1108,12 +1108,7 @@ int pid_compare_func(const void *a, const void *b) {
         const pid_t *p = a, *q = b;
 
         /* Suitable for usage in qsort() */
-
-        if (*p < *q)
-                return -1;
-        if (*p > *q)
-                return 1;
-        return 0;
+        return CMP(*p, *q);
 }
 
 int ioprio_parse_priority(const char *s, int *ret) {