fix timezone parser code crashing on 64bit sys

if sizeof(time_t) == 8, this code path was missing the correct
offset into the zoneinfo file, using the header magic to do
offset calculations.
the 6 32bit fields to be read start at offset 20.
timezone parser: fix offset to transition table in 64bit code path

we need to skip to the second TZif header, which starts at
skip+44, and then skip another header (20 bytes) plus the following
6 32bit values.
timezone parser: fix iteration over search dir paths

try+l points to \0, so only one iteration was ever tried.