waterDayYear() failing again (#223, #237) on CRAN for several R-devel architectures.

This may not be specifically related to R-devel changes, as our regular tests pass on GHA, but rather likely related to the locale the tests are being run in combined with recent R-devel changes to date/time related functions

  ── Failure (test-waterDayYear.R:15:3): works as expected ───────────────────────
  res.lr$wd not equal to 153L.
  1/1 mismatches
  [1] 152 - 153 == -1
  ── Failure (test-waterDayYear.R:16:3): works as expected ───────────────────────
  res$wd not equal to 152L.
  1/1 mismatches
  [1] 151 - 152 == -1
  ── Failure (test-waterDayYear.R:23:3): works as expected ───────────────────────
  res$wd not equal to 1.
  1/1 mismatches
  [1] 0 - 1 == -1
  ── Failure (test-waterDayYear.R:30:3): works as expected ───────────────────────
  res$wd not equal to 365.
  1/1 mismatches
  [1] 364 - 365 == -1
  ── Failure (test-waterDayYear.R:38:3): works as expected ───────────────────────
  res$wd not equal to c(50, 140).
  2/2 mismatches (average diff: 1)
  [1] 49 - 50 == -1
  [2] 139 - 140 == -1

R-devel related changes:

• The as.POSIXlt(<POSIXlt>) and as.POSIXct(<POSIXct>) default methods now do obey their tz argument, also in this case.

• as.POSIXlt(<Date>) now does apply a tz (timezone) argument, as does as.POSIXct(); partly suggested by Roland Fuß on the R-devel mailing list.

• as.Date.POSIXct(., tz) now treats several ‘tz’ values, notably ‘"GMT"’ as equivalent to ‘"UTC"’, proposed and improved by Michael Chirico and Joshua Ulrich in PR#17674.

• as.POSIXct(<numeric>) and as.POSIXlt(.) (without specifying ‘origin’) now work. So does as.Date(<numeric>), too.

• As ‘"POSIXlt"’ objects may be “partially filled” and their list components meant to be recycled, ‘length()’ now is the length of the longest component.