Bug #704185: GnuCash 2.5 doesn't build on FreeBSD

Undefined symbols 'timezone' and 'daylight'
These are declared extern globals in time.h on most Unices, but not
on some BSDs. Since they're not used anywhere in Gnucash, just delete
setting them.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23106 57a11ea4-9604-0410-9ed3-97b8803252fd