Added dlna_src_use_time_range() which is similar to dlna_src_use_byte_range() to simplify the if statements in code.
Made dlna_src_use_time_range() cleaner for now.  Might need to split apart in the future due to availableSeekRange support.
Merge pull request #18 from cablelabs/add-use-time-method

Added dlna_src_use_time_range() which is similar to dlna_src_use_byte_ra...