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/cliloop.c

@@ -0,0 +1,125 @@
+#include <errno.h>
+
+#include "putty.h"
+
+void cli_main_loop(cliloop_pw_setup_t pw_setup,
+                   cliloop_pw_check_t pw_check,
+                   cliloop_continue_t cont, void *ctx)
+{
+    unsigned long now = GETTICKCOUNT();
+
+    int *fdlist = NULL;
+    size_t fdsize = 0;
+
+    pollwrapper *pw = pollwrap_new();
+
+    while (true) {
+        int rwx;
+        int ret;
+        int fdstate;
+        unsigned long next;
+
+        pollwrap_clear(pw);
+
+        if (!pw_setup(ctx, pw))
+            break; /* our client signalled emergency exit */
+
+        /* Count the currently active fds. */
+        size_t nfds = 0;
+        for (int fd = first_fd(&fdstate, &rwx); fd >= 0;
+             fd = next_fd(&fdstate, &rwx))
+            nfds++;
+
+        /* Expand the fdlist buffer if necessary. */
+        sgrowarray(fdlist, fdsize, nfds);
+
+        /*
+         * Add all currently open uxsel fds to pw, and store them in
+         * fdlist as well.
+         */
+        size_t fdcount = 0;
+        for (int fd = first_fd(&fdstate, &rwx); fd >= 0;
+             fd = next_fd(&fdstate, &rwx)) {
+            fdlist[fdcount++] = fd;
+            pollwrap_add_fd_rwx(pw, fd, rwx);
+        }
+
+        if (toplevel_callback_pending()) {
+            ret = pollwrap_poll_instant(pw);
+        } else if (run_timers(now, &next)) {
+            do {
+                unsigned long then;
+                long ticks;
+
+                then = now;
+                now = GETTICKCOUNT();
+                if (now - then > next - then)
+                    ticks = 0;
+                else
+                    ticks = next - now;
+
+                bool overflow = false;
+                if (ticks > INT_MAX) {
+                    ticks = INT_MAX;
+                    overflow = true;
+                }
+
+                ret = pollwrap_poll_timeout(pw, ticks);
+                if (ret == 0 && !overflow)
+                    now = next;
+                else
+                    now = GETTICKCOUNT();
+            } while (ret < 0 && errno == EINTR);
+        } else {
+            ret = pollwrap_poll_endless(pw);
+        }
+
+        if (ret < 0 && errno == EINTR)
+            continue;
+
+        if (ret < 0) {
+            perror("poll");
+            exit(1);
+        }
+
+        bool found_fd = (ret > 0);
+
+        for (size_t i = 0; i < fdcount; i++) {
+            int fd = fdlist[i];
+            int rwx = pollwrap_get_fd_rwx(pw, fd);
+            /*
+             * We must process exceptional notifications before
+             * ordinary readability ones, or we may go straight
+             * past the urgent marker.
+             */
+            if (rwx & SELECT_X)
+                select_result(fd, SELECT_X);
+            if (rwx & SELECT_R)
+                select_result(fd, SELECT_R);
+            if (rwx & SELECT_W)
+                select_result(fd, SELECT_W);
+        }
+
+        pw_check(ctx, pw);
+
+        bool ran_callback = run_toplevel_callbacks();
+
+        if (!cont(ctx, found_fd, ran_callback))
+            break;
+    }
+
+    pollwrap_free(pw);
+    sfree(fdlist);
+}
+
+bool cliloop_no_pw_setup(void *ctx, pollwrapper *pw) { return true; }
+void cliloop_no_pw_check(void *ctx, pollwrapper *pw) {}
+bool cliloop_always_continue(void *ctx, bool fd, bool cb) { return true; }
+
+/*
+ * Any application using this main loop doesn't need to do anything
+ * when uxsel adds or removes an fd, because we synchronously re-check
+ * the current list every time we go round the main loop above.
+ */
+uxsel_id *uxsel_input_add(int fd, int rwx) { return NULL; }
+void uxsel_input_remove(uxsel_id *id) { }