Implementation of user-level fault handler

This pull request is intended to get feedback of the implementation of fault handler.

Core related changes:

Implemented 7 different fault handlers in the llbooter. When a fault happens the system will make a sinv call to the llbooter to handle the fault. Made an allocation of the sinv_cap of these fault handlers in the llbooter. The location of these sinv_caps in the captbl of each component have been hardcoded in cos_types.h.
Changed the sret_ret to make sure the system will use iret instead of sysexit when dealing with a fault. The registers will be restored before the fault is returned. I have added a 'fault_flag' in the invstk push and pop function to tell the sret_ret it is a normal sinv or a sinv of a fault handler.
Changed the exception.c file to save the fault regs and make a sinv call to the user-level fault handler. I have added a function called fault_handler_sinv which basically intended to reduce the redundancy of the code.

Now the user-level fault handler returns without and operation so the fault will repeat. I plan to kill the faulting thread to 'handle' the fault.

Choose one (Mandatory):

[x] This PR is for a code-review and is intended to get feedback, but not to be pulled yet.
[ ] This PR is mature, and ready to be integrated into the repo.

@gparmer , @hungry-foolish , @phanikishoreg

As part of this pull request, I've considered the following:

[Style]

[x] Comments adhere to the Style Guide (SG)
[x] Spacing adhere's to the SG
[x] Naming adhere's to the SG
[x] All other aspects of the SG are adhered to, or exceptions are justified in this pull request
[ ] I have run the auto formatter on my code before submitting this PR (see doc/auto_formatter.md for instructions)

[Code Craftsmanship]:

[x] I've made an attempt to remove all redundant code
[x] I've considered ways in which my changes might impact existing code, and cleaned it up
[x] I've formatted the code in an effort to make it easier to read (proper error handling, function use, etc...)
[ ] I've commented appropriately where code is tricky
[ ] I agree that there is no "throw-away" code, and that code in this PR is of high quality

I've tested the code using the following test programs (provide list here):

gwsystems / composite