tree-wide: use ALPHANUMERICAL where appropriate

Prompted by 43116c5662

src/basic/env-util.c

@@ -19,7 +19,7 @@
 
 /* We follow bash for the character set. Different shells have different rules. */
 #define VALID_BASH_ENV_NAME_CHARS               \
-        DIGITS LETTERS                          \
+        ALPHANUMERICAL                          \
         "_"
 
 size_t sc_arg_max(void) {

src/basic/login-util.c

@@ -10,7 +10,7 @@ bool session_id_valid(const char *id) {
         if (isempty(id))
                 return false;
 
-        return id[strspn(id, LETTERS DIGITS)] == '\0';
+        return in_charset(id, ALPHANUMERICAL);
 }
 
 bool logind_running(void) {

src/basic/unit-name.c

@@ -17,8 +17,7 @@
 
 /* Characters valid in a unit name. */
 #define VALID_CHARS                             \
-        DIGITS                                  \
-        LETTERS                                 \
+        ALPHANUMERICAL                          \
         ":-_.\\"
 
 /* The same, but also permits the single @ character that may appear */