various: move const ptr indicator to return value

src/basic/virt.h

@@ -65,6 +65,6 @@ Virtualization detect_virtualization(void);
 int running_in_userns(void);
 int running_in_chroot(void);
 
-const char *virtualization_to_string(Virtualization v) _const_;
+const char* virtualization_to_string(Virtualization v) _const_;
 Virtualization virtualization_from_string(const char *s) _pure_;
 bool has_cpu_with_flag(const char *flag);