* cygtls.h: Add more "don't parse this" guards.

* cygtls.h: Add more "don't parse this" guards.
(_threadinfo::init_thread): Rename from 'init'.
(_threadinfo::init): Declare new function.
(_threadinfo::protect_linked_list): Declare new critical section.
* dcrt0.cc (dll_crt0_1): Call init_thread to initialize thread stuff.
(_dll_crt0): Call _threadinfo::init prior to invoking dll_crt0_1.
* exceptions.cc (_threadinfo::init_thread): Rename from 'init'.
(_threadinfo::init): Define new function.  Protect linked list manipulation
with new critical section.
(_threadinfo::call): Reflect function name change.
(_threadinfo::remove): Protect linked list manipulation with new critical
section
* gentls_offsets: Rework to allow multi-line "don't parse this" protection.
* init.cc (dll_entry): Don't remove threads info stuff here since the remove
function uses a critical section which can't be used during thread creation or
destruction.
* thread.cc (pthread::exit): Call _threadinfo remove function here.