tree-wide: use path_startswith() rather than startswith() where ever that's appropriate

When checking path prefixes we really should use the right APIs, just in
case people add multiple slashes to their paths...

src/basic/terminal-util.c

@@ -55,6 +55,7 @@
 #include "terminal-util.h"
 #include "time-util.h"
 #include "util.h"
+#include "path-util.h"
 
 static volatile unsigned cached_columns = 0;
 static volatile unsigned cached_lines = 0;
@@ -556,6 +557,7 @@ int terminal_vhangup(const char *name) {
 
 int vt_disallocate(const char *name) {
         _cleanup_close_ int fd = -1;
+        const char *e, *n;
         unsigned u;
         int r;
 
@@ -563,7 +565,8 @@ int vt_disallocate(const char *name) {
          * (i.e. because it is the active one), at least clear it
          * entirely (including the scrollback buffer) */
 
-        if (!startswith(name, "/dev/"))
+        e = path_startswith(name, "/dev/");
+        if (!e)
                 return -EINVAL;
 
         if (!tty_is_vc(name)) {
@@ -582,10 +585,11 @@ int vt_disallocate(const char *name) {
                 return 0;
         }
 
-        if (!startswith(name, "/dev/tty"))
+        n = startswith(e, "tty");
+        if (!n)
                 return -EINVAL;
 
-        r = safe_atou(name+8, &u);
+        r = safe_atou(n, &u);
         if (r < 0)
                 return r;