This patch provides user with a better hint when most RTS options
are not available (not compiled with -rtsopts).
A new field "rtsOptsEnabled" is added into RtsFlags.MiscFlags to
tell the availablity of RTS options.
- Unlike other flag fields in "libraries/base/GHC/RTS/Flags.hsc",
"RtsOptsEnabled" is defined in "includes/RtsAPI.h" and lacks constant macros.
Therefore In "GHC.RTS", "RtsOptsEnabled" simply derives Enum instance and reads as of type "CInt".
I don't know if this is a proper way to deal with it.
- There are other ways to change RTS options (e.g. -with-rtsopts),
but it might be too verbose to mention.
- I'm not sure how to trigger the error message about "maximum number of censuses reached",
therefore no testcase for that particular case.
- In the ticket @rwbarton proposed about addinng an option "-no-rtsopts-suggestions",
which is not implemented in this patch.