Shell: Allow parts of globs to be named in match expressions

This patchset allows a match expression to have a list of names for its
glob parts, which are assigned to the matched values in the body of the
match.
For example,
```sh
stuff=foobarblahblah/target_{1..30}
for $stuff {
    match $it {
        */* as (dir sub) {
            echo "doing things with $sub in $dir"
            make -C $dir $sub # or whatever...
        }
    }
}
```

With this, match expressions are now significantly more powerful!

Shell/Tests/match.sh

@@ -51,3 +51,33 @@ match "$(echo)" {
 };
 
 test "$result" = yes || echo invalid result $result for string subst match && exit 1
+
+match (foo bar) {
+    (f? *) as (x y) {
+        result=fail
+    }
+    (f* b*) as (x y) {
+        if [ "$x" = oo -a "$y" = ar ] {
+            result=yes
+        } else {
+            result=fail
+        }
+    }
+}
+
+test "$result" = yes || echo invalid result $result for subst match with name && exit 1
+
+match (foo bar baz) {
+    (f? * *z) as (x y z) {
+        result=fail
+    }
+    (f* b* *z) as (x y z) {
+        if [ "$x" = oo -a "$y" = ar -a "$z" = ba ] {
+            result=yes
+        } else {
+            result=fail
+        }
+    }
+}
+
+test "$result" = yes || echo invalid result $result for subst match with name 2 && exit 1