Move proxy-related source files into a subdirectory.

There are quite a few of them already, and I'm about to make another
one, so let's start with a bit of tidying up.

The CMake build organisation is unchanged: I haven't put the proxy
object files into a separate library, just moved the locations of the
source files. (Organising proxying as a library would be tricky
anyway, because of the various overrides for tools that want to avoid
cryptography.)

unix/CMakeLists.txt

@@ -138,7 +138,7 @@ if(GTK_FOUND)
     x11.c
     noise.c
     ${CMAKE_SOURCE_DIR}/ssh/x11fwd.c
-    ${CMAKE_SOURCE_DIR}/nosshproxy.c)
+    ${CMAKE_SOURCE_DIR}/proxy/nosshproxy.c)
   target_link_libraries(pageant
     eventloop console agent settings network crypto utils
     ${GTK_LIBRARIES})
@@ -149,7 +149,7 @@ if(GTK_FOUND)
     main-gtk-simple.c
     ${CMAKE_SOURCE_DIR}/be_none.c
     ${CMAKE_SOURCE_DIR}/nogss.c
-    ${CMAKE_SOURCE_DIR}/nosshproxy.c
+    ${CMAKE_SOURCE_DIR}/proxy/nosshproxy.c
     pty.c)
   target_link_libraries(pterm
     guiterminal eventloop settings charset utils
@@ -162,7 +162,7 @@ if(GTK_FOUND)
     ${CMAKE_SOURCE_DIR}/nocmdline.c
     ${CMAKE_SOURCE_DIR}/be_none.c
     ${CMAKE_SOURCE_DIR}/nogss.c
-    ${CMAKE_SOURCE_DIR}/nosshproxy.c
+    ${CMAKE_SOURCE_DIR}/proxy/nosshproxy.c
     pty.c)
   target_link_libraries(ptermapp
     guiterminal eventloop settings charset utils
@@ -196,8 +196,8 @@ if(GTK_FOUND)
     ${CMAKE_SOURCE_DIR}/be_nos_s.c
     ${CMAKE_SOURCE_DIR}/nogss.c
     ${CMAKE_SOURCE_DIR}/norand.c
-    ${CMAKE_SOURCE_DIR}/nocproxy.c
-    ${CMAKE_SOURCE_DIR}/nosshproxy.c)
+    ${CMAKE_SOURCE_DIR}/proxy/nocproxy.c
+    ${CMAKE_SOURCE_DIR}/proxy/nosshproxy.c)
   target_link_libraries(puttytel
     guiterminal eventloop otherbackends settings network charset utils
     ${GTK_LIBRARIES} ${X11_LIBRARIES})

unix/local-proxy.c

@@ -12,7 +12,7 @@
 #include "tree234.h"
 #include "putty.h"
 #include "network.h"
-#include "proxy.h"
+#include "proxy/proxy.h"
 
 Socket *platform_new_connection(SockAddr *addr, const char *hostname,
                                 int port, bool privport,

unix/sharing.c

@@ -16,7 +16,7 @@
 #include "tree234.h"
 #include "putty.h"
 #include "network.h"
-#include "proxy.h"
+#include "proxy/proxy.h"
 #include "ssh.h"
 
 #define CONNSHARE_SOCKETDIR_PREFIX "/tmp/putty-connshare"