Fix parser::parse_names() which fails on pattern inclusion groups for some corner cases

Specifically, fix the function for the case when the pattern inclusion group
is specified first in the pattern group in a directory. For example, before
the fix, compiling the following buildfile:

fs = hello
exe{hello}: foo/{hxx ixx txx cxx}{+{$fs}}

would fail with the following error:

invalid 'foo/hello' in name pattern

1 files changed, 12 insertions, 0 deletions

diff --git a/tests/name/pattern.testscript b/tests/name/pattern.testscript
index c1a4ce4..efd15b2 100644
--- a/tests/name/pattern.testscript
+++ b/tests/name/pattern.testscript
@@ -153,6 +153,9 @@ EOI
   mkdir bar;
   $* <'print {f*/ +{b*/}}' >/'bar/'                : include-group
 
+  mkdir -p foo/bar;
+  $* <'print $path.canonicalize(foo/{+{b*/}})' >/'foo/bar/' : include-group-first
+
   touch foo.txt fox.txt;
   $* <'print {*.txt -f*.txt +*x.txt}' >'fox.txt'   : include-exclude-order
 
@@ -309,6 +312,15 @@ EOI
     print {+{$pats}}
     EOI
 
+  : pattern-via-expansion-list-subdir
+  :
+  mkdir baz;
+  touch baz/foo.txt baz/bar.hxx;
+  $* <<EOI >'baz/bar.hxx baz/foo.txt'
+    pats = '*.hxx' '*.txt'
+    print baz/{+{$pats}}
+    EOI
+
   : pattern-via-expansion-type
   :
   touch foo.txt;