REORG: include: move THREAD_LOCAL and __decl_thread() to compiler.h

REORG: include: move THREAD_LOCAL and __decl_thread() to compiler.h

Since these are used as type attributes or conditional clauses, they
are used about everywhere and should not require a dependency on
thread.h. Moving them to compiler.h along with other similar statements
like ALIGN() etc looks more logical; this way they become part of the
base API. This allowed to remove thread-t.h from ~12 files, one was
found to only require thread-t and not thread and dict.c was found to
require thread.h.