Fix latent bug in custom word point completion handling

Without this fix, if we switch the "print" completer to custom word
point handling, we regress gdb.base/completion.exp like this:

 (gdb) p "break1.c FAIL: gdb.base/completion.exp: complete 'p "break1' (timeout)

The problem is that completing an expression that starts with double
quotes, and resolves to a filename, like this:

 (gdb) p "break1[TAB]

would change from this, with current master:

 (gdb) p "break1.c"|
         ^^^^^^^^^^|
                   \- cursor here

to this:

 (gdb) p "break1.c |
         ^^^^^^^^^^|
                   \- quote replaced by space

The issue is that completer.c:advance_to_completion_word misses
telling the completion tracker to emulate readline's handling of
completing a string when rl_find_completion_word returns a delimiter.

This commit fixes the latent bug.

gdb/ChangeLog:
2019-06-13  Pedro Alves  <palves@redhat.com>

	* completer.c (advance_to_completion_word): Handle delimiters.

1 files changed, 8 insertions, 1 deletions

diff --git a/gdb/completer.c b/gdb/completer.c
index d4773f2..03d0d0e 100644
--- a/gdb/completer.c
+++ b/gdb/completer.c
@@ -365,11 +365,18 @@ advance_to_expression_complete_word_point (completion_tracker &tracker,
   info.quote_characters = gdb_completer_quote_characters;
   info.basic_quote_characters = rl_basic_quote_characters;
 
+  int delimiter;
   const char *start
-    = gdb_rl_find_completion_word (&info, NULL, NULL, text);
+    = gdb_rl_find_completion_word (&info, NULL, &delimiter, text);
 
   tracker.advance_custom_word_point_by (start - text);
 
+  if (delimiter)
+    {
+      tracker.set_quote_char (delimiter);
+      tracker.set_suppress_append_ws (true);
+    }
+
   return start;
 }