Patch to solve compatibility issue between flex 2.6.3

Issue/feature addressed

There is a compatibility issue between flex 2.6.3 and the scotch library causing the following compilation error: undefined reference to `scotchyywrap'.

Proposed solution

The problem can be solved by a minor modification of the parser_ll.l while using third party scotch 6.0.4.

Implementation

A patch file and a modified cmake/ThirdPartyScotch.cmake file are used to modify the build/ThirdParty/scotch-6.0.4/src/libscotch/parser_ll.l file at compilation.

Tests

Notes

None

Checklist

• Functions and classes, or changes to them, are documented.
• User guide/documentation is updated.
• Changelog is updated.
• Suitable tests added for new functionality.
• Contributed code is correctly formatted. (See the contributing guidelines).
• License added to any new files.
• No extraneous files have been added (e.g. compiler output or test data files).

Warning

On the 19.07 the code formatting (code style) was standardised using clang-format, over the whole Nektar++ code. This means changes in your branch will conflict with formatting changes on the master branch. To resolve these conflicts , see #295 (closed)