osl_setSystemLocale was introduced with af293834
"#88460# added osl_getProcessLocale and osl_setProcessLocale" but never actually
used.  So mark it as deprecated and, in the sal/osl/unx/ case, don't make it
set the OS-level locale via imp_setProcessLocale (calling setlocale or setting
the LC_ALL/LC_CTYPE/LANG env vars), same as in the sal/osl/w32/ case.

Change-Id: I33348dba5de8ca80ca6fca210043286c0cfa9145