feat: warning if file setup parameters are ignored

[jodavies]

If file setup parameters (#: ...) are provided, but there are non-comment lines preceeding them, they are silently ignored. This is consistent with the manual, but easy to do by accident. Add a warning in this case.

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This is not perfect, in that it won't catch things like

#: MaxTermSize 50K
#define TEST "10"
#: SmallSize 1G

but it will catch (probably) most instances of this.

[coveralls]

coverage: 63.202% (+0.02%) from 63.186% — jodavies:file-late-setup into form-dev:master

[jodavies]

Updated version, which also warns in cases like

#: MaxTermSize 50K
#define TEST "10"
#: SmallSize 1G