Orphan instances detection in haskell-process-trigger-suggestions is outdated

I can't be certain, but it looks like orphan instance warning have changed in recent versions of GHC. Currently `haskell-process-trigger-suggestions` function uses following regex to detect orphan instance warnings in compiler response `"Warning: orphan instance: "` [[1](https://github.com/haskell/haskell-mode/blob/322782edfb3603911431e75d171fad9a9dfe6ff4/haskell-load.el#L153)], while GHC 7.10.3 gives a bit different formatting:

```
/Users/oman/dev/haskell/sol/solitaire/src/Solitaire.hs:12:10: Warning:
Orphan instance: instance Show Layer
To avoid this
move the instance declaration to the module of the class or of the type, or
wrap the type with a newtype and declare the instance on the new type.
```

As a result, `haskell-process-trigger-suggestions` does not suggest to add OPTIONS pragma as intended.

@gracjan I know we need tests for this function, it's quite big and good test suite should rely on genuine GHC response, what will you say?