Suppress warning on certain unknown pragmas (Was: Overlapping and incoherent instances)

[Henning Thielemann]

Am 29.07.2014 um 14:13 schrieb Richard Eisenberg:

> I think one nice thing about this proposal is that it doesn't seem (to me) to require CPP around the pragma: unrecognized pragmas are warned about but are otherwise harmless. Are folks very keen to have *warning-free* compilation on several GHC versions?

I'd prefer to tell GHC, to not warn about a given list of pragmas. E.g. 
I would have liked to tell GHC-7.4 about the new MINIMAL pragma that I 
added to some of my libraries. There might also be pragmas used for 
other tools or compilers that GHC should ignore.