kernel/x86_64: add ia32 syscall entry and commpage syscall code.

* only for Intel sysenter/sysexit.
* the entry function processes stack arguments as follows:
we look up the syscall in the table

kernel/x86_64: add ia32 syscall entry and commpage syscall code.

* only for Intel sysenter/sysexit.
* the entry function processes stack arguments as follows:
we look up the syscall in the table, find the number of arguments.
reserve place on the stack for the arguments.
copy arguments on the stack
pop register arguments
call the syscall function
place the return value in ax and dx registers.
* TODO: we need to store the arguments somewhere for the post-syscall tracing.
* the thread exit stub is 32-bit, for the time being use hexadecimal instructions.

Change-Id: Ie5c502eb596d4fa7613d238de80643566bc19ed8

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