tree-wide: move unsigned to the start of type declaration

Even though ISO C11 doesn't mandate in which order the type specifiers
should appear, having `unsigned` at the beginning of each type
declaration feels more natural and, more importantly, it unbreaks
Coccinelle, which has a hard time parsing `long unsigned` and others:

```
init_defs_builtins: /usr/lib64/coccinelle/standard.h
init_defs: /home/mrc0mmand/repos/systemd/coccinelle/macros.h
HANDLING: src/shared/mount-util.c
: 1: strange type1, maybe because of weird order: long unsigned
```

Most of the codebase already "complies", so let's fix the remaining
"offenders".

src/basic/parse-util.c

@@ -415,7 +415,7 @@ int safe_atoi(const char *s, int *ret_i) {
         return 0;
 }
 
-int safe_atollu_full(const char *s, unsigned base, long long unsigned *ret_llu) {
+int safe_atollu_full(const char *s, unsigned base, unsigned long long *ret_llu) {
         char *x = NULL;
         unsigned long long l;