Global variables shouldn't be allowed to contain operators in their value expressions

[mewore]

For example, having this at the first line of a file is invalid:

integer BASELINE = 5006 + 512 + 512;

The LSL plugin doesn't report an error:

• NOTE: Not only operators, but also function calls, etc., may be disallowed
• I think syntax errors can be confusing and it may be better to parse everything liberally first and then show specific errors like "operators are not allowed in the definitions of global variables" or, in the case of custom states being declared above the default one, "the default state should be declared before all other states"