Fix MS-Windows build --with-modules

Fix MS-Windows build --with-modules

* src/module.c: Reformat copyright commentary.
(module_vec_get): Use explicit cast to size_t to avoid compiler
warning in 32-bit builds.
(check_main_thread) [WINDOWSNT]: Fix letter-case in Windows APIs.
Compare thread IDs directly, as GetThreadId is not available
before Windows Vista.
(check_main_thread) [WINDOWSNT]: Duplicate the thread handle
without using APIs and constants not available on XP and older
systems.  Obtain and store the thread ID as well.