[zeditor] ZScript shouldn't prompt to save changes when no changes were made

Steps to recreate:

1. File->New
2. ZScript->Compile ZScript...; 9-button "Compile ZScript" window appears
3. Click 'Edit'; white 'Edit ZScript' window appears with #include "std.zh"
4. Press ESC
5. Observe "Save changes to buffer?" Yes/No msgbox appears

This msgbox could cause novice scripters to become paranoid that they accidentally modified their script when that isn't the case.

Similarly, we can probably skip the "Confirm Overwrite" msgbox when clicking 'Load' in that 9-button window when '#include "std.zh"' is the only thing in the buffer.