Add the dynamic linker name and fix a type name to use the public name
instead of the glibc internal name.

gcc/ChangeLog:

2019-11-15  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* config/m68k/linux.h (MUSL_DYNAMIC_LINKER): Define.

libgcc/ChangeLog:

2019-11-15  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* config/m68k/linux-unwind.h (struct uw_ucontext): Use sigset_t instead
	of __sigset_t.

From-SVN: r278312