Improve sleigh error reporting

[kkaempf]

This improves error reporting from the sleigh language parser.

• making the calc_mask() size parameter unsigned prevents sleigh from just crashing with

terminate called after throwing an instance of 'std::out_of_range'
  what():  map::at
Aborted (core dumped)

• the other commit adds location information to sleigh error messages, improving the above error to

vax.slaspec:379 - ERROR Error: Pattern size cannot vary (missing '...'?): for table "instruction" constructor starting at line 373

No output produced

[ghidracadabra]

Thanks for submitting this, I'll take a look.

One thing to note is that there is also a java sleigh compiler ghidra.pcodeCPort.slgh_compile.SleighCompile which should also have the new error messages.

If java's not your thing I can add them myself.

[kkaempf]

Oh, two sleigh compiler implementations 🙈 Time to drop one ? 🤔 I'll see what I can do but I'm not a Java programmer.