[Ada] array pointers encoded as typedef to fat pointer

A recent change in check_typedef caused the following regression,
considering:

        type String_Access is access String;
        S1 : String_Access := null;

Trying to print S1, we get:

        (gdb) print s1
        $1 = (string) (null)

The type name is wrong.  We were expecting:

        (gdb) print s1
        $1 = (string_bug.string_access) (null)

The extensive comment in this patch explains how pointers to arrays
are encoded when the array is a "fat pointer".  What happened is
that the change in check_typedef broke a type-equality test that
we were performing.   The test really was on the fringe, but it
turns out that, for what we're doing, we're really only interested
in the main-type portion of the type.

The patch adjust the check accordingly.

gdb/ChangeLog:

        * ada-lang.c (ada_to_fixed_type): Expand function documentation.
        Return the original type if the main type portions match rather
         than when the type themselves match.

1 files changed, 6 insertions, 0 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 8872ab4..dd91159 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2010-11-22  Joel Brobecker  <brobecker@adacore.com>
 
+	* ada-lang.c (ada_to_fixed_type): Expand function documentation.
+	Return the original type if the main type portions match rather
+	than when the type themselves match.
+
+2010-11-22  Joel Brobecker  <brobecker@adacore.com>
+
 	* ada-lang.c (ada_template_to_fixed_record_type_1):
 	For dynamic fields, check the field size against the maximum
 	object size.