Fixes from Janko Richter <jankorichter@yahoo.de>

- Fix wrong index results on text, char, varchar for multibyte strings
- Fix some SIGFPE signals
- Add support for infinite timestamps
- Because of locale settings, btree_gist can not be a prefix index anymore (for text).
  Each node holds now just the lower and upper boundary.

contrib/btree_gist/data/timestamptz.data

@@ -393,6 +393,12 @@
 2004-01-28 20:45:12 GMT+0
 1991-03-21 13:23:37 GMT-5
 2029-07-26 06:01:08 GMT+9
+infinity
+infinity
+infinity
+infinity
+infinity
+infinity
 2002-11-15 19:24:22 GMT
 1987-05-02 16:25:01 GMT-6
 1999-04-01 05:54:41 GMT-2
@@ -422,6 +428,12 @@
 1984-10-17 02:42:50 GMT-7
 2001-04-29 03:59:54 GMT-1
 1996-08-15 07:16:34 GMT-3
+infinity
+infinity
+infinity
+infinity
+infinity
+infinity
 \N
 1974-02-10 02:40:01 GMT-11
 2033-03-28 21:51:56 GMT+10
@@ -475,6 +487,12 @@
 1973-06-15 06:34:08 GMT-11
 1976-03-21 22:21:06 GMT-10
 1976-06-15 07:14:46 GMT-10
+-infinity
+-infinity
+-infinity
+-infinity
+-infinity
+-infinity
 1972-01-15 06:30:22 GMT-11
 1971-08-06 10:41:43 GMT-11
 1995-08-21 21:12:06 GMT-3