Move obsolescent Montreal entry to 'backward'.

This is like the previous change, except it entails a change to zone.tab.
The America/Montreal entry was created only because we mistakenly
thought that Montreal's and Toronto's post-1970 time stamps differed.
* backward, northamerica (America/Montreal):
Now a 'backward' link to America/Toronto.
* northamerica (Mont): Remove rules; no longer needed.
(America/Thunder_Bay): Refer to Toronto rules, not Mont.
This doesn't change any time stamps.
* zone.tab (America/Montreal): Remove.
(America/Toronto): Say that it also covers most of Quebec.

backward

@@ -34,6 +34,7 @@ Link	America/Kentucky/Louisville	America/Louisville
 Link	America/Puerto_Rico	America/Lower_Princes
 Link	America/Puerto_Rico	America/Marigot
 Link	America/Argentina/Mendoza	America/Mendoza
+Link	America/Toronto		America/Montreal
 Link	America/Puerto_Rico	America/Montserrat
 Link	America/Toronto		America/Nassau
 Link	America/Puerto_Rico	America/Port_of_Spain

northamerica

@@ -1342,8 +1342,8 @@ Zone America/Moncton	-4:19:08 -	LMT	1883 Dec  9
 # Quebec
 
 # From Paul Eggert (2013-08-26):
-# Shanks & Pottenger write that since 1970 most of Quebec has been
-# like Montreal.
+# Since 1970 most of Quebec has been like Toronto.
+# See America/Toronto.
 
 # Matthews and Vincent (1998) also write that Quebec east of the -63
 # meridian is supposed to observe AST, but residents as far east as
@@ -1359,46 +1359,6 @@ Zone America/Moncton	-4:19:08 -	LMT	1883 Dec  9
 # Shanks & Pottenger who have this region observing AST/ADT.
 # See America/Puerto_Rico.
 
-# Rule	NAME	FROM	TO	TYPE	IN	ON	AT	SAVE	LETTER/S
-Rule	Mont	1917	only	-	Mar	25	2:00	1:00	D
-Rule	Mont	1917	only	-	Apr	24	0:00	0	S
-Rule	Mont	1919	only	-	Mar	31	2:30	1:00	D
-Rule	Mont	1919	only	-	Oct	25	2:30	0	S
-Rule	Mont	1920	only	-	May	 2	2:30	1:00	D
-Rule	Mont	1920	1922	-	Oct	Sun>=1	2:30	0	S
-Rule	Mont	1921	only	-	May	 1	2:00	1:00	D
-Rule	Mont	1922	only	-	Apr	30	2:00	1:00	D
-Rule	Mont	1924	only	-	May	17	2:00	1:00	D
-Rule	Mont	1924	1926	-	Sep	lastSun	2:30	0	S
-Rule	Mont	1925	1926	-	May	Sun>=1	2:00	1:00	D
-# The 1927-to-1937 rules can be expressed more simply as
-# Rule	Mont	1927	1937	-	Apr	lastSat	24:00	1:00	D
-# Rule	Mont	1927	1937	-	Sep	lastSat	24:00	0	S
-# The rules below avoid use of 24:00
-# (which pre-1998 versions of zic cannot handle).
-Rule	Mont	1927	only	-	May	1	0:00	1:00	D
-Rule	Mont	1927	1932	-	Sep	lastSun	0:00	0	S
-Rule	Mont	1928	1931	-	Apr	lastSun	0:00	1:00	D
-Rule	Mont	1932	only	-	May	1	0:00	1:00	D
-Rule	Mont	1933	1940	-	Apr	lastSun	0:00	1:00	D
-Rule	Mont	1933	only	-	Oct	1	0:00	0	S
-Rule	Mont	1934	1939	-	Sep	lastSun	0:00	0	S
-Rule	Mont	1946	1973	-	Apr	lastSun	2:00	1:00	D
-Rule	Mont	1945	1948	-	Sep	lastSun	2:00	0	S
-Rule	Mont	1949	1950	-	Oct	lastSun	2:00	0	S
-Rule	Mont	1951	1956	-	Sep	lastSun	2:00	0	S
-Rule	Mont	1957	1973	-	Oct	lastSun	2:00	0	S
-
-# Zone	NAME		GMTOFF	RULES	FORMAT	[UNTIL]
-Zone America/Montreal	-4:54:16 -	LMT	1884
-			-5:00	Mont	E%sT	1918
-			-5:00	Canada	E%sT	1919
-			-5:00	Mont	E%sT	1942 Feb  9 2:00s
-			-5:00	Canada	E%sT	1946
-			-5:00	Mont	E%sT	1974
-			-5:00	Canada	E%sT
-
-
 # Ontario
 
 # From Paul Eggert (2006-07-09):
@@ -1619,7 +1579,7 @@ Zone America/Thunder_Bay -5:57:00 -	LMT	1895
 			-6:00	-	CST	1910
 			-5:00	-	EST	1942
 			-5:00	Canada	E%sT	1970
-			-5:00	Mont	E%sT	1973
+			-5:00	Toronto	E%sT	1973
 			-5:00	-	EST	1974
 			-5:00	Canada	E%sT
 Zone America/Nipigon	-5:53:04 -	LMT	1895

zone.tab

@@ -122,8 +122,7 @@ CA	+4612-05957	America/Glace_Bay	Atlantic Time - Nova Scotia - places that did n
 CA	+4606-06447	America/Moncton	Atlantic Time - New Brunswick
 CA	+5320-06025	America/Goose_Bay	Atlantic Time - Labrador - most locations
 CA	+5125-05707	America/Blanc-Sablon	Atlantic Standard Time - Quebec - Lower North Shore
-CA	+4531-07334	America/Montreal	Eastern Time - Quebec - most locations
-CA	+4339-07923	America/Toronto	Eastern Time - Ontario - most locations
+CA	+4339-07923	America/Toronto	Eastern Time - Ontario & Quebec - most locations
 CA	+4901-08816	America/Nipigon	Eastern Time - Ontario & Quebec - places that did not observe DST 1967-1973
 CA	+4823-08915	America/Thunder_Bay	Eastern Time - Thunder Bay, Ontario
 CA	+6344-06828	America/Iqaluit	Eastern Time - east Nunavut - most locations