Update time zone data files to tzdata release 2018f.

DST law changes in Chile, Fiji, and Russia (Volgograd).
Historical corrections for China, Japan, Macau, and North Korea.

Note: like the previous tzdata update, this involves a depressingly
large amount of semantically-meaningless churn in tzdata.zi.  That
is a consequence of upstream's data compression method assigning
unstable abbreviations to DST rulesets.  I complained about that
to them last time, and this version now uses an assignment method
that pays some heed to not changing abbreviations unnecessarily.
So hopefully, that'll be better going forward.

src/timezone/known_abbrevs.txt

@@ -92,6 +92,7 @@ NZST	43200
 PDT	-25200	D
 PKT	18000
 PST	-28800
+PST	28800
 SAST	7200
 SST	-39600
 UCT	0

src/timezone/tznames/America.txt

@@ -237,6 +237,9 @@ PDT    -25200 D  # Pacific Daylight Time
 PET    -18000    # Peru Time (obsolete)
 PMDT    -7200 D  # Pierre & Miquelon Daylight Time (obsolete)
 PMST   -10800    # Pierre & Miquelon Standard Time (obsolete)
+# CONFLICT! PST is not unique
+# Other timezones:
+#  - PST: Philippine Standard Time
 PST    -28800    # Pacific Standard Time
                  #     (America/Dawson)
                  #     (America/Los_Angeles)

src/timezone/tznames/Asia.txt

@@ -158,6 +158,10 @@ PKT     18000    # Pakistan Time
                  #     (Asia/Karachi)
 PKST    21600 D  # Pakistan Summer Time
                  #     (Asia/Karachi)
+# CONFLICT! PST is not unique
+# Other timezones:
+#  - PST: Pacific Standard Time (America)
+PST     28800    # Philippine Standard Time
 QYZT    21600    # Kizilorda Time (obsolete)
 SAKST   Asia/Sakhalin  # Sakhalin Summer Time (obsolete)
 SAKT    Asia/Sakhalin  # Sakhalin Time (obsolete)

src/timezone/tznames/Default

@@ -181,6 +181,9 @@ PDT    -25200 D  # Pacific Daylight Time
                  #     (America/Whitehorse)
 PMDT    -7200 D  # Pierre & Miquelon Daylight Time (obsolete)
 PMST   -10800    # Pierre & Miquelon Standard Time (obsolete)
+# CONFLICT! PST is not unique
+# Other timezones:
+#  - PST: Philippine Standard Time
 PST    -28800    # Pacific Standard Time
                  #     (America/Dawson)
                  #     (America/Los_Angeles)

src/timezone/tznames/Pacific.txt

@@ -52,6 +52,9 @@ NZST    43200    # New Zealand Standard Time
 PGT     36000    # Papua New Guinea Time (obsolete)
 PHOT    Pacific/Enderbury  # Phoenix Islands Time (Kiribati) (obsolete)
 PONT    39600    # Ponape Time (Micronesia) (obsolete)
+# CONFLICT! PST is not unique
+# Other timezones:
+#  - PST: Philippine Standard Time
 PST    -28800    # Pacific Standard Time
                  #     (America/Dawson)
                  #     (America/Los_Angeles)