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.

unix/local-proxy.c

@@ -0,0 +1,105 @@
+/*
+ * uxproxy.c: Unix implementation of platform_new_connection(),
+ * supporting an OpenSSH-like proxy command.
+ */
+
+#include <stdio.h>
+#include <assert.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "tree234.h"
+#include "putty.h"
+#include "network.h"
+#include "proxy.h"
+
+Socket *platform_new_connection(SockAddr *addr, const char *hostname,
+                                int port, bool privport,
+                                bool oobinline, bool nodelay, bool keepalive,
+                                Plug *plug, Conf *conf)
+{
+    char *cmd;
+
+    int to_cmd_pipe[2], from_cmd_pipe[2], cmd_err_pipe[2], pid, proxytype;
+    int infd, outfd, inerrfd;
+
+    proxytype = conf_get_int(conf, CONF_proxy_type);
+    if (proxytype != PROXY_CMD && proxytype != PROXY_FUZZ)
+        return NULL;
+
+    if (proxytype == PROXY_CMD) {
+        cmd = format_telnet_command(addr, port, conf);
+
+        {
+            char *logmsg = dupprintf("Starting local proxy command: %s", cmd);
+            plug_log(plug, PLUGLOG_PROXY_MSG, NULL, 0, logmsg, 0);
+            sfree(logmsg);
+        }
+
+        /*
+         * Create the pipes to the proxy command, and spawn the proxy
+         * command process.
+         */
+        if (pipe(to_cmd_pipe) < 0 ||
+            pipe(from_cmd_pipe) < 0 ||
+            pipe(cmd_err_pipe) < 0) {
+            sfree(cmd);
+            return new_error_socket_fmt(plug, "pipe: %s", strerror(errno));
+        }
+        cloexec(to_cmd_pipe[1]);
+        cloexec(from_cmd_pipe[0]);
+        cloexec(cmd_err_pipe[0]);
+
+        pid = fork();
+        if (pid == 0) {
+            close(0);
+            close(1);
+            dup2(to_cmd_pipe[0], 0);
+            dup2(from_cmd_pipe[1], 1);
+            close(to_cmd_pipe[0]);
+            close(from_cmd_pipe[1]);
+            dup2(cmd_err_pipe[1], 2);
+            noncloexec(0);
+            noncloexec(1);
+            execl("/bin/sh", "sh", "-c", cmd, (void *)NULL);
+            _exit(255);
+        }
+
+        sfree(cmd);
+
+        if (pid < 0)
+            return new_error_socket_fmt(plug, "fork: %s", strerror(errno));
+
+        close(to_cmd_pipe[0]);
+        close(from_cmd_pipe[1]);
+        close(cmd_err_pipe[1]);
+
+        outfd = to_cmd_pipe[1];
+        infd = from_cmd_pipe[0];
+        inerrfd = cmd_err_pipe[0];
+    } else {
+        cmd = format_telnet_command(addr, port, conf);
+        outfd = open("/dev/null", O_WRONLY);
+        if (outfd == -1) {
+            sfree(cmd);
+            return new_error_socket_fmt(
+                plug, "/dev/null: %s", strerror(errno));
+        }
+        infd = open(cmd, O_RDONLY);
+        if (infd == -1) {
+            Socket *toret = new_error_socket_fmt(
+                plug, "%s: %s", cmd, strerror(errno));
+            sfree(cmd);
+            close(outfd);
+            return toret;
+        }
+        sfree(cmd);
+        inerrfd = -1;
+    }
+
+    /* We are responsible for this and don't need it any more */
+    sk_addr_free(addr);
+
+    return make_fd_socket(infd, outfd, inerrfd, plug);
+}