More preparatory work: remove the <windows.h> include from lots of

source files in which it's no longer required (it was previously
required in anything that included <putty.h>, but not any more).
Also moved a couple of stray bits of exposed WinSock back into
winnet.c (getservbyname from ssh.c and AF_INET from proxy.c).

[originally from svn r2160]

unix/unix.h

@@ -42,4 +42,7 @@ void provide_xrm_string(char *string);
 
 #define DEFAULT_CODEPAGE 0	       /* FIXME: no idea how to do this */
 
+#define strnicmp strncasecmp
+#define stricmp strcasecmp
+
 #endif