Pragmas in student code could break requirements checking

As discussed in #1059:

When requirements are being checked, the DynFlags from the current GHC compilation are used when parsing student code and templates, but that means that LANGUAGE and OPTIONS_GHC pragmas from the current module are included in these flags.

This has the potential to cause some issues, as it means that student source code could affect parsing, possibly changing the interpretation of certain requirements or causing them to fail to parse properly.