Proposal: Add setEnv/unsetEnv to "base"

Hi, setting environment variables is possible on both POSIX and Windows systems. Currently this functionally is missing from System.Environment; the "unix" package provides an implementation for POSIX systems. I propose to add setEnv/unsetEnv to System.Environment, so that it is easier to write applications that behave the same on POSIX and Windows systems. I implemented both in a way, so that they behave exactly the same on POSIX and Windows (modulo case sensitivity on Windows). For now I prepared a standalone implementation [1] and corresponding tests [2]. That implementation depends on the "unix" package. If the proposal is accepted, I will prepare a patch against "base" that includes the relevant code from "unix". Discussion Period: 2 Weeks Cheers, Simon [1] https://github.com/sol/setenv/blob/master/src/System/SetEnv.hs [2] https://github.com/sol/setenv/blob/master/test/System/SetEnvSpec.hs