Modified the default accept range value to be false unless bytes is explicitly specified.  Added dlna_src_is_range_supported() and dlna_src_is_dtcp_range_supported() to explicitly check if server supports Range or Range.dtcp.com headers.  Added a check in dlna_src_adjust_http_src_headers() to make sure dtcp encrypted content supports Range.dtcp.com for byte based seeks.  Added logic to exclude range header if not supported.  Issue a second head request for dtcp encrypted content that supports Range.dtcp.com and also to make sure range is supported prior to issuing second head with range header.  Print out info log if second head request is not sent.
Merge pull request #57 from cablelabs/dtcp-range-fix

Modified the default accept range value to be false unless bytes is expl...