Back-patch src/timezone/known_abbrevs.txt into all active branches.

Needed so that timezone data update patches can be cherry-picked
into older branches conveniently.

src/timezone/known_abbrevs.txt

+ADDT	-7200	D
+ADT	-10800	D
+ADT	14400	D
+AFT	16200
+AKST	-32400
+ALMST	25200	D
+AMT	-14400
+AMT	14400
+ANAT	39600
+APT	-10800	D
+AQTT	14400
+AQTT	18000
+ART	-10800
+AST	-14400
+AST	10800
+AWT	-10800	D
+AZOT	-3600
+AZST	18000	D
+BDST	25200	D
+BEAT	9000
+BEAUT	9900
+BNT	28800
+BOT	-14400
+BRT	-10800
+BTT	21600
+CAST	10800	D
+CAT	7200
+CCT	23400
+CDT	-14400	D
+CDT	-18000	D
+CDT	32400	D
+CEST	7200	D
+CET	3600
+CHAST	45900
+CHOT	28800
+CHUT	36000
+CIT	28800
+CKHST	-34200	D
+CLT	-14400
+COT	-18000
+CPT	-18000	D
+CST	-21600
+CST	28800
+CST	34200
+CVT	-3600
+CWST	31500
+CWT	-18000	D
+CXT	25200
+ChST	36000
+DAVT	25200
+DDUT	36000
+EASST	-18000	D
+EAT	10800
+ECT	-18000
+EDT	-14400	D
+EEST	10800	D
+EET	7200
+EGST	0	D
+EPT	-14400	D
+EST	-18000
+EST	36000
+FET	10800
+FJT	43200
+FKST	-10800
+FNT	-7200
+GALT	-21600
+GAMT	-32400
+GET	14400
+GFT	-10800
+GILT	43200
+GMT	0
+GMT+1	-3600
+GMT+10	-36000
+GMT+11	-39600
+GMT+12	-43200
+GMT+2	-7200
+GMT+3	-10800
+GMT+4	-14400
+GMT+5	-18000
+GMT+6	-21600
+GMT+7	-25200
+GMT+8	-28800
+GMT+9	-32400
+GMT-1	3600
+GMT-10	36000
+GMT-11	39600
+GMT-12	43200
+GMT-13	46800
+GMT-14	50400
+GMT-2	7200
+GMT-3	10800
+GMT-4	14400
+GMT-5	18000
+GMT-6	21600
+GMT-7	25200
+GMT-8	28800
+GMT-9	32400
+GST	-7200
+GST	14400
+GYT	-14400
+HAST	-36000
+HOVT	25200
+HST	-36000
+ICT	25200
+ICT	28800
+IDDT	14400	D
+IOT	21600
+IRDT	16200	D
+IRKT	32400
+IST	23400	D
+JST	32400
+KDT	36000	D
+KGT	21600
+KOST	43200
+KRAT	28800
+KST	28800
+LHST	39600	D
+LINT	50400
+LKT	21600
+MAGT	43200
+MART	-34200
+MAWT	18000
+MDT	-21600	D
+MET	3600
+MHT	43200
+MIST	39600
+MMT	23400
+MPT	-21600	D
+MSK	14400
+MST	-25200
+MUT	14400
+MVT	18000
+MWT	-21600	D
+MYT	28800
+MeST	-28800
+NCT	39600
+NDDT	-5400	D
+NFT	41400
+NOVST	25200	D
+NOVT	25200
+NPT	20700
+NRT	43200
+NUT	-39600
+NZST	43200
+OMST	25200
+ORAT	18000
+PDT	-25200	D
+PET	-18000
+PETT	39600
+PGT	36000
+PHOT	46800
+PKT	18000
+PMDT	-7200	D
+PONT	39600
+PPT	-25200	D
+PST	-28800
+PWT	32400
+PYST	-10800	D
+QYZT	21600
+RET	14400
+ROTT	-10800
+SAKT	36000
+SAMT	10800
+SAST	10800	D
+SAST	7200
+SBT	39600
+SCT	14400
+SGT	28800
+SRT	-10800
+SST	-39600
+SYOT	10800
+TAHT	-36000
+TFT	18000
+TJT	18000
+TKT	46800
+TMT	18000
+TOST	50400	D
+TVT	43200
+UCT	0
+ULAT	28800
+UTC	0
+UYHST	-9000	D
+UZT	18000
+VET	-14400
+VLAT	39600
+VOLT	10800
+VOST	21600
+VUT	39600
+WAKT	43200
+WARST	-10800	D
+WART	-14400
+WAST	7200	D
+WAT	-3600
+WAT	0
+WAT	3600
+WEST	3600	D
+WET	0
+WFT	43200
+WGST	-7200	D
+WIT	25200
+WST	28800
+WST	46800
+YAKT	36000
+YEKT	21600