Caveats in variable naming and conflicts

[elektito]

The following cases should be added to vars.test file, and pass.

Duplicate definition:
x% = 10
dim x as

Duplicate definition:
dim x as single
x% = 2

Duplicate definition:
dim x a s single
print x%

No error; x and x! are the same variable:
dim x as sinle
x! = 2

No error; x and x% are separate variables:
dim x
x% = 2

No error; x and x! are the same variable:
dim x
x! = 5