runtime: Fix defer of unlock thread at program startup.

Don't free stack allocated defer block.  Also ensure we have a
Go context in a few more places before freeing the block.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@205940 138bc75d-0d04-0410-961f-82ee72b054a4
compiler: Tweak untyped nil error message.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@205941 138bc75d-0d04-0410-961f-82ee72b054a4