libc: don't take alien thread for main pthread

It covers bugs which we should detect and fix, especially depending on
the result of pthread_myself locking implementation (ours and vbox) takes
decision to take a lock or just to assume it is a reentrant locking attempt.

Fixes #1128
vbox: remove patches regarding ioport width check

Issue #1129
nova: mtd fields are unsigned

Bit 31 (FPU Mtd) got negative expanded when combined with 64bit value.

Detected during work on #1129
vmm: parameterize Vcpu_dispatcher

Pre-condition to realize #1129, to be able to let a vCPU handler thread also
be a pthread.
fixup "vmm: parameterize Vcpu_dispatcher"
vbox: join emt and vcpu handler thread

Fixes #1129