Sha384 (#38)

* Added SHA384

* Remove the RR32 and RR64

Both of the mentioned functions simply rename Rotate_Right. To increase
readability this commit removes both functions. Affected modules are
SHA256 and SHA512.

* Rename TS64 to Big_Endian_Unpack

This commit renames TS64 to Big_Endian_Unpack and propagates this change
to the modules implementing SHA256 and SHA512. Additionally,
Big_Endian_Get_Byte ghost function is added to prove the post condition
of the Big_Endian_Unpack.

* Replace TS64 with Big_Endian_Unpack in SHA384 pkg

This commit replaces the TS64 function with the Big_Endian_Unpack
function. Both functions are functionally identical but differ in their
implementation and what is proved about them.

* ReWIP: factored common SHA384, SHA512 code into parent packagage, tests pass still need to run proofs

* SHA384, moved common functions to SHA2_Common pkg

* Workaround for GNAT 14 codegen issue

* Discharged proofs

* Added Loop_Variant to prove subprogram termination

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Co-authored-by: mxar <[email protected]>

Update to version 4.0.0 and GNAT >= 12.1.1

Move constants and declarations to libary level to avoid multiple ela…

…boration of them. Remove inner block statement in * operator.

Remove unnecessary local variables. Proof and tests all OK and improv…

…es performance at -O0

Revert to original implementation of * as basis for performance test …

…against new_mul branch

Carchup merge branch 'master' into new_mul

Add correct dependency for GNAT >= 11.2.1

Add pragma Warnings to deal with wording change produced by SPARK Com…

…munity 2021

Unroll first iteration of main loop in *, and merge with initializati…

…on of T. A bit faster at all optimization levels.

Remove lookup tables for CSwap16 and CSwap32 and replace with a simpl…

…er expression.