pthread_create: TLS alignment and cleanup

pthread_create: TLS alignment and cleanup

This patch replaces 2 function calls from musl with
2 custom ones and introduces an additional size
when allocating the map for a thread, `libc.tls_align`.
It is needed because Unikraft demands that the tls be aligned.

Signed-off-by: Dragos Iulian Argint <dragosargint21@gmail.com>
Reviewed-by: Florin Postolache <florin.postolache80@gmail.com>
Reviewed-by: Simon Kuenzer <simon@unikraft.io>
Reviewed-by: Cezar Craciunoiu <cezar.craciunoiu@unikraft.io>
Reviewed-by: Razvan Deaconescu <razvand@unikraft.io>
Reviewed-by: Robert Kuban <robert.kuban@opensynergy.com>
Approved-by: Simon Kuenzer <simon@unikraft.io>
Tested-by: Unikraft CI <monkey@unikraft.io>
GitHub-Closes: #9