Complete support for 2-pass compile

[MatthewHambley]

Only GFortran supported at the moment. Need fuller support.

[t00sa]

Two-pass compilation is largely working but there are a few outstanding issues to resolve:

• [ ] minor bug(s) related to messages (@hiker may have a fix for these)
• [ ] Intel compilers overwrite existing mod files, resulting in potential corruption when building in parallel
• [ ] add CCE support but this is dependent on access to the most recent versions of the compiler