Fix handling of relocations against TLS section symbols.

Fix handling of relocations against TLS section symbols.

Gold doesn't handle relocations against the section symbol for a TLS
section correctly. Instead of using the offset of the section relative
to the TLS segment, it uses the address of the actual section.  This
patch checks for section symbols for TLS sections, and treats them
the same as TLS symbols.

gold/
	PR gold/16773
	* object.cc (Sized_relobj_file): Compute value of section symbols
	for TLS sections the same as TLS symbols.