gdb/testsuite: fix gdb.ada/complete.exp timeout in READ1 mode

While reviewing another patch I spotted a timeout in
gdb.ada/complete.exp when testing in READ1 mode, e.g.:

  $ make check-read1 TESTS="gdb.ada/complete.exp"
  ...
  FAIL: gdb.ada/complete.exp: complete break ada (timeout)
  ...

The problem is an attempt to match the entire output from GDB within a
single gdb_test_multiple pattern, for a completion command that
returns a large number of completions.

This commit changes the gdb_test_multiple to process the output line
by line.  I don't use the gdb_test_multiple -lbl option, as I've
always found that option backward -- it checks for the \r\n at the
start of each line rather than the end, I think it's much clearer to
use '^' at the start of each pattern, and '\r\n' at the end, so that's
what I've done here.

.... Or I would, if this test didn't already define $eol as the end of
line regexp ... except that $eol was set to '[\r\n]*', which isn't
that helpful, so I've updated $eol to be just '\r\n' the actual end of
line regexp.

And now, the test passes without a timeout when using READ1.

There should be no change in what is tested after this commit.

Approved-By: Tom Tromey <tom@tromey.com>

gdb/testsuite/gdb.ada/complete.exp

@@ -28,7 +28,7 @@ clean_restart ${testfile}
 set bp_location [gdb_get_line_number "START" ${testdir}/foo.adb]
 runto "foo.adb:$bp_location"
 
-set eol "\[\r\n\]*"
+set eol "\r\n"
 
 # A convenience function that verifies that the "complete EXPR" command
 # returns the EXPECTED_OUTPUT.
@@ -227,11 +227,20 @@ test_gdb_complete "ambiguous_func" \
 gdb_test_no_output "set max-completions unlimited"
 
 set test "complete break ada"
-gdb_test_multiple "$test" $test {
-    -re "^$test$eol\(break ada\[\]\[a-z0-9._@/-\]*$eol\)+$gdb_prompt $" {
-        pass $test
+gdb_test_multiple $test "" {
+    -re "^($test$eol)" {
+	exp_continue
     }
+
+    -re "^(break ada\[\]\[a-z0-9._@/-\]*$eol)" {
+	exp_continue
+    }
+
+    -re "^$gdb_prompt $" {
+	pass $gdb_test_name
+    }
+
     -re "\[A-Z\].*$gdb_prompt $" {
-	fail "$test (gdb/22670)"
+	fail "$gdb_test_name (gdb/22670)"
     }
 }