Docs: Clarify that isMinTTY only checks for old MinTTYs

Despite the name, `isMinTTY` is only capable of detecting the presence of old
versions of MinTTY. The name of the function is perhaps misleading in that
regard, but it is widely used enough at this point to where renaming it would
be disruptive. Instead, let's just clarify its intent in the documentation.

Resolves #216.

Author: RyanGlScott

System/Win32/MinTTY.hsc

@@ -15,7 +15,12 @@
 -- Stability   :  provisional
 -- Portability :  portable
 --
--- A function to check if the current terminal uses MinTTY.
+-- A function to check if the current terminal uses an old version of MinTTY
+-- that emulates a TTY. Note, however, that this does not check for more recent
+-- versions of MinTTY that use the native Windows console PTY directly. The old
+-- approach (where MinTTY emulates a TTY) sometimes requires different
+-- approaches to handling keyboard inputs.
+--
 -- Much of this code was originally authored by Phil Ruffwind and the
 -- git-for-windows project.
 --
@@ -50,8 +55,9 @@ import Foreign.C.Types
 #include <windows.h>
 #include "winternl_compat.h"
 
--- | Returns 'True' if the current process's standard error is attached to a
--- MinTTY console (e.g., Cygwin or MSYS). Returns 'False' otherwise.
+-- | Returns 'True' if the current process's standard error is attached to an
+-- emulated MinTTY console (e.g., Cygwin or MSYS that use an old version of
+-- MinTTY). Returns 'False' otherwise.
 isMinTTY :: IO Bool
 isMinTTY = do
     h <- getStdHandle sTD_ERROR_HANDLE
@@ -61,8 +67,9 @@ isMinTTY = do
        then return False
        else isMinTTYHandle h
 
--- | Returns 'True' is the given handle is attached to a MinTTY console
--- (e.g., Cygwin or MSYS). Returns 'False' otherwise.
+-- | Returns 'True' is the given handle is attached to an emulated MinTTY
+-- console (e.g., Cygwin or MSYS that use an old version of MinTTY). Returns
+-- 'False' otherwise.
 isMinTTYHandle :: HANDLE -> IO Bool
 isMinTTYHandle h = do
     fileType <- getFileType h