Handle preExp and varDecls for crefs with subs.

[mahge]

• This fixes ticket:5994.

• We used to throw away any extra expressions and variable declarations
  needed for crefs with (complicated) subscripts, i.e., if it has some complicated
  subscript that can not be generated inline.

• If you are sure you have a path (a cref with no subs) then you can use
  contextCrefNoPrevExp (e.g. variable names are just paths. They are just
  represented as cref). Otherwise contextCref now needs a preExp and varDecls
  buffer passed to it.

• Avoid unnecessary code generation.

  • The path we took for crefs with subscripts in function context
    used to create unnecessary temporaries and expressions which we did
    not notice because they were were thrown away after being created.

  • Split up the LHS cref generation template function to take different paths for
    normal and parallel functions.

• Add a test case for Ticket:5994.

• Remaining issues

  • There are still cases where cref code generation does not get all needed information
    like buffers and correct context. This needs to be updated.
  • Generation of LHS crefs for parmodelica parallel functions needs to be updated
    for recent changes.
  • contextCrefOld template function needs to be removed after replacing its uses by
    contextCref or an appropriate function.

[sjoelund]

Add a reference to ticket:5994 in a commit message

[mahge]

@sjoelund Will do. This is not over yet. I am trying to see if these changes (which are mostly renaming and parameter additions) broke anything. Just to to simplify things.

The actual fix comes on the next commit/s