Add UID-based APIs:

Add UID-based APIs:
const char* tzplatform_uid_getenv(uid_t uid, enum tzplatform_variable id);
const char* tzplatform_uid_mkpath(uid_t uid, enum tzplatform_variable id, const char *path);
const char* tzplatform_uid_mkpath3(uid_t uid, enum tzplatform_variable id, const char *path, const char *path2);
const char* tzplatform_uid_mkpath4(uid_t uid, enum tzplatform_variable id, const char *path, const char *path2, const char *path3);

Change-Id: I5f81ce6ed46bb97021b174486bef6c236edb61b2
Signed-off-by: Hyotaek Shim <hyotaek.shim@samsung.com>