fix several bugs in array type handling in dotnet module

[vthib]

Several bugs were present in the parsing and generation of a string to represent an array type, notably when the "lo_bound" value is set.

• The "read_blob_signed" was buggy for values outside the [-2**6, 2**6-1], the sign edition did not use the right bitmask, and the type used was unsigned.

• The display when lo_bound != 0 was buggy:

  • size=5, lobound=0 => should be 5, this was ok
  • size=5, lobound=1 => should be 1...5, this was buggy and displayed 1...6. The "range format" is inclusive.

• 0 should still be displayed if size is 0. Only when size is unset should it be left out. So an array declared as [5,0,3] should be displayed the same way, and not as [5,,3].

[plusvic]

@vthib do you have some .NET files that trigger these issues. I want to have some reference files and check that this is correctly done on YARA-X as well.

[vthib]

Yes, I crafted some files for testing in boreal, one of which test array sizes: types2.dll

lo bound values on arrays cannot be used in C# files afaik, but they can easily be tested with MSIL files. The aforementioned file was generated from this source code: types2.cil

This makes it easy to compare the syntax used in the MSIL file with the type strings generated in the yara module.

[vthib]

I fixed an unnecessary change, should be ok now