Remove spurious space

Andres Freund
Add new timezone abbrevation "FET".

This seems to have been invented in 2011 to represent GMT+3, non daylight
savings rules, as now used in Europe/Kaliningrad and Europe/Minsk.
There are no conflicts so might as well add it to the Default list.
Per bug #7804 from Ruslan Izmaylov.
Reject out-of-range dates in to_date().

Dates outside the supported range could be entered, but would not print
reasonably, and operations such as conversion to timestamp wouldn't behave
sanely either.  Since this has the potential to result in undumpable table
data, it seems worth back-patching.

Hitoshi Harada
Fix obsolete SQL syntax in comment.

This was legal back in the days of add_missing_from, though perhaps
never good style.  It's not legal anymore ...

Jan Urbański
Return value of lseek() can be negative on failure.

Because the return value of lseek() was assigned to an unsigned size_t
variable, we'd fail to notice an error return code -1. Compiler gave a
warning about this.

Andres Freund
Fix hash_update_hash_key() to handle same-bucket case correctly.

Original coding would corrupt the hashtable if the item being updated was
at the end of its bucket chain and the new hash key hashed to that same
bucket.  Diagnosis and fix by Heikki Linnakangas.