[PATCH] psql: Make ParseVariableDouble reject values above max

Hello,

ParseVariableDouble() in src/bin/psql/variables.c is asymmetric in how
it handles the [min, max] bounds it documents. The lower-bound branch
correctly returns false, but the upper-bound branch logs the error and
then falls through to assign *result and return true. The function's
contract ("the value must be within the range [min,max] in order to be
considered valid"; "if unsuccessful, *result isn't clobbered") is
broken on the upper-bound path.

The only caller today is watch_interval_hook, so the user-visible
effect is that an out-of-range WATCH_INTERVAL is reported as invalid
yet still assigned.

Reproducer:

$ psql
# \set WATCH_INTERVAL 99999999
invalid value "99999999" for variable "WATCH_INTERVAL": must be less than
1000000.00
# \echo :WATCH_INTERVAL
99999999
The error is printed, but the variable is set anyway.

Regards,
Sven Klemm