[settings] use timezone settings for all supported posix platforms except of android

According to Frodo code for TZ settings they handled for all \_LINUX platforms not including TARGET\_ANDROID and AppleTV2 with iOS < 4.3 (see https://github.com/xbmc/xbmc/blob/Frodo/xbmc/settings/GUISettings.cpp#L1424)
Withal \_LINUX defined for all posix platforms, and TARGET\_POSIX defined for them too (see https://github.com/xbmc/xbmc/blob/Frodo/configure.in#L551)
The patch adds TZ handling for TARGET\_POSIX && !TARGET\_ANROID. See #4095 and a2f3ca2 for more details.
I made it blind so help needed from platform devs.