[WRAPPERS] Add a isSimpleWrapper function for RV64

[rajdakin]

This PR adds support for the isSimpleWrapper function on RISC-V 64. It also adds a default function returning 0 if the architecture is unsupported (i.e. not ARM or RISC-V).
There is also minor fixes in the script (the "free letters" comment does not contain x and X, an error message was incorrect, and a type hint was invalid for mypy).
The first commit contains the entire change, the second contains only a version bump.

[ksco]

We’re filtering all the sign-extended ones for RV64? This makes the simple functions set much smaller than AArch64, but it’s a start to enable this feature I think.

[ksco]

A more complicated proposal: make isSimpleWrapper return a uint64_t and every 2-bits indicates the width of the current sign-extended parameter/return value:

00 -> not sign-extended
01 -> signed char
10 -> short
11 -> int

[ptitSeb]

A more complicated proposal: make isSimpleWrapper return a uint64_t and every 2-bits indicates the width of the current sign-extended parameter/return value:

00 -> not sign-extended
01 -> signed char
10 -> short
11 -> int

Return value is already used to check float / double stuff iirc.