[exim] code aesthetics

Dear eximers!

compiling 4.94 on my old i386/linux-2.4 box ( ¡it works! ) I stumbled upon too
points, which are probably more aesthetical nowadays, but anyhow:

a) a simple typo

--- OS/os.h-Linux.orig  2020-05-30 22:35:38.000000000 +0200
+++ OS/os.h-Linux       2020-06-17 14:13:39.000000000 +0200
@@ -71,7 +71,7 @@
 # define LLONG_MAX LONG_LONG_MAX
 #endif

-#if _POSIX_C_SOURCE >= 200809L || _ATFILE_SOUCE
+#if _POSIX_C_SOURCE >= 200809L || _ATFILE_SOURCE
# define EXIM_HAVE_OPENAT
#endif

b) although OS/os.h-Linux ( may ) define ``EXIM_HAVE_OPENAT'', at several
   places the functions linkat/openat are used without #ifdef'ing them:
     src/functions.h        -> leads to ``implicit definition'' warnings
     src/transports/queuefile.c

regards

Horst Wente