Rename most of the platform source files.

This gets rid of all those annoying 'win', 'ux' and 'gtk' prefixes
which made filenames annoying to type and to tab-complete. Also, as
with my other recent renaming sprees, I've taken the opportunity to
expand and clarify some of the names so that they're not such cryptic
abbreviations.

windows/select-cli.c

@@ -0,0 +1,78 @@
+/*
+ * Implementation of do_select() for winnet.c to use, suitable for use
+ * when there's no GUI window to have network activity reported to.
+ *
+ * It uses WSAEventSelect, where available, to convert network
+ * activity into activity on an event object, for integration into an
+ * event loop that includes WaitForMultipleObjects.
+ *
+ * It also maintains a list of currently active sockets, which can be
+ * retrieved by a front end that wants to use WinSock's synchronous
+ * select() function.
+ */
+
+#include "putty.h"
+
+static tree234 *winselcli_sockets;
+
+static int socket_cmp(void *av, void *bv)
+{
+    return memcmp(av, bv, sizeof(SOCKET));
+} 
+
+HANDLE winselcli_event = INVALID_HANDLE_VALUE;
+
+void winselcli_setup(void)
+{
+    if (!winselcli_sockets)
+        winselcli_sockets = newtree234(socket_cmp);
+
+    if (p_WSAEventSelect && winselcli_event == INVALID_HANDLE_VALUE)
+        winselcli_event = CreateEvent(NULL, false, false, NULL);
+}
+
+SOCKET winselcli_unique_socket(void)
+{
+    if (!winselcli_sockets)
+        return INVALID_SOCKET;
+
+    assert(count234(winselcli_sockets) <= 1);
+
+    SOCKET *p = index234(winselcli_sockets, 0);
+    if (!p)
+        return INVALID_SOCKET;
+
+    return *p;
+}
+
+const char *do_select(SOCKET skt, bool enable)
+{
+    /* Check everything's been set up, for convenience of callers. */
+    winselcli_setup();
+
+    if (enable) {
+        SOCKET *ptr = snew(SOCKET);
+        *ptr = skt;
+        if (add234(winselcli_sockets, ptr) != ptr)
+            sfree(ptr);                /* already there */
+    } else {
+        SOCKET *ptr = del234(winselcli_sockets, &skt);
+        if (ptr)
+            sfree(ptr);
+    }
+
+    if (p_WSAEventSelect) {
+        int events;
+        if (enable) {
+            events = (FD_CONNECT | FD_READ | FD_WRITE |
+                      FD_OOB | FD_CLOSE | FD_ACCEPT);
+        } else {
+            events = 0;
+        }
+
+        if (p_WSAEventSelect(skt, winselcli_event, events) == SOCKET_ERROR)
+            return winsock_error_string(p_WSAGetLastError());
+    }
+
+    return NULL;
+}