users-guide: Fix a few markup issues

Strangely these were only causing the build to fail in the aarch64-linux
job, despite Sphinx throwing errors in all jobs I checked.

Also changes some `#ifdef`s to `#if defined` to satisfy the linter.

docs/users_guide/ffi-chap.rst

@@ -87,7 +87,7 @@ Newtype wrapping of the IO monad
 The FFI spec requires the IO monad to appear in various places, but it
 can sometimes be convenient to wrap the IO monad in a ``newtype``, thus: ::
 
-      newtype MyIO a = MIO (IO a)
+       newtype MyIO a = MIO (IO a)
 
 (A reason for doing so might be to prevent the programmer from calling
 arbitrary IO procedures in some part of the program.)
@@ -112,15 +112,15 @@ The type variables in the type of a foreign declaration may be quantified with
 an explicit ``forall`` by using the :extension:`ExplicitForAll` language
 extension, as in the following example: ::
 
-    {-# LANGUAGE ExplicitForAll #-}
-    foreign import ccall "mmap" c_mmap :: forall a. CSize -> IO (Ptr a)
+       {-# LANGUAGE ExplicitForAll #-}
+       foreign import ccall "mmap" c_mmap :: forall a. CSize -> IO (Ptr a)
 
 Note that an explicit ``forall`` must appear at the front of the type signature
 and is not permitted to appear nested within the type, as in the following
 (erroneous) examples: ::
 
-    foreign import ccall "mmap" c_mmap' :: CSize -> forall a. IO (Ptr a)
-    foreign import ccall quux :: (forall a. Ptr a) -> IO ()
+       foreign import ccall "mmap" c_mmap' :: CSize -> forall a. IO (Ptr a)
+       foreign import ccall quux :: (forall a. Ptr a) -> IO ()
 
 .. _ffi-prim:
 
@@ -372,7 +372,7 @@ program. Here's the C code:
     #include <stdio.h>
     #include "HsFFI.h"
 
-    #ifdef __GLASGOW_HASKELL__
+    #if defined(__GLASGOW_HASKELL__)
     #include "Foo_stub.h"
     #endif
 
@@ -391,7 +391,7 @@ program. Here's the C code:
     }
 
 We've surrounded the GHC-specific bits with
-``#ifdef __GLASGOW_HASKELL__``; the rest of the code should be portable
+``#if defined(__GLASGOW_HASKELL__)``; the rest of the code should be portable
 across Haskell implementations that support the FFI standard.
 
 The call to ``hs_init()`` initializes GHC's runtime system. Do NOT try
@@ -435,7 +435,7 @@ GHC-specific API instead of ``hs_init()``:
     #include <stdio.h>
     #include "HsFFI.h"
 
-    #ifdef __GLASGOW_HASKELL__
+    #if defined(__GLASGOW_HASKELL__)
     #include "Foo_stub.h"
     #include "Rts.h"
     #endif

docs/users_guide/ghci.rst

@@ -2582,21 +2582,22 @@ commonly used commands.
     For example:
 
     .. code-block:: none
-      >:instances Maybe (Maybe Int)
-      instance Eq (Maybe (Maybe Int)) -- Defined in ‘GHC.Maybe’
-      instance Ord (Maybe (Maybe Int)) -- Defined in ‘GHC.Maybe’
-      instance Show (Maybe (Maybe Int)) -- Defined in ‘GHC.Show’
-      instance Read (Maybe (Maybe Int)) -- Defined in ‘GHC.Read’
-
-      >:set -XPartialTypeSignatures -fno-warn-partial-type-signatures
-
-      >:instances Maybe _
-      instance Eq _ => Eq (Maybe _) -- Defined in ‘GHC.Maybe’
-      instance Semigroup _ => Monoid (Maybe _) -- Defined in ‘GHC.Base’
-      instance Ord _ => Ord (Maybe _) -- Defined in ‘GHC.Maybe’
-      instance Semigroup _ => Semigroup (Maybe _) -- Defined in ‘GHC.Base’
-      instance Show _ => Show (Maybe _) -- Defined in ‘GHC.Show’
-      instance Read _ => Read (Maybe _) -- Defined in ‘GHC.Read’
+
+         > :instances Maybe (Maybe Int)
+         instance Eq (Maybe (Maybe Int)) -- Defined in ‘GHC.Maybe’
+         instance Ord (Maybe (Maybe Int)) -- Defined in ‘GHC.Maybe’
+         instance Show (Maybe (Maybe Int)) -- Defined in ‘GHC.Show’
+         instance Read (Maybe (Maybe Int)) -- Defined in ‘GHC.Read’
+
+         > :set -XPartialTypeSignatures -fno-warn-partial-type-signatures
+
+         > :instances Maybe _
+         instance Eq _ => Eq (Maybe _) -- Defined in ‘GHC.Maybe’
+         instance Semigroup _ => Monoid (Maybe _) -- Defined in ‘GHC.Base’
+         instance Ord _ => Ord (Maybe _) -- Defined in ‘GHC.Maybe’
+         instance Semigroup _ => Semigroup (Maybe _) -- Defined in ‘GHC.Base’
+         instance Show _ => Show (Maybe _) -- Defined in ‘GHC.Show’
+         instance Read _ => Read (Maybe _) -- Defined in ‘GHC.Read’
 
 .. ghci-cmd:: :main; ⟨arg1⟩ ... ⟨argn⟩