Make 'LogContext' a typedef visible throughout the code.

Same principle again - the more of these structures have globally
visible tags (even if the structure contents are still opaque in most
places), the fewer of them I can mistake for each other.

unix/gtkwin.c

@@ -162,7 +162,7 @@ struct gui_data {
     Backend *back;
     void *backhandle;
     Terminal *term;
-    void *logctx;
+    LogContext *logctx;
     int exited;
     struct unicode_data ucsdata;
     Conf *conf;

unix/uxcons.c

@@ -405,7 +405,7 @@ void old_keyfile_warning(void)
     postmsg(&cf);
 }
 
-void console_provide_logctx(void *logctx)
+void console_provide_logctx(LogContext *logctx)
 {
     console_logctx = logctx;
 }

unix/uxpgnt.c

@@ -92,7 +92,7 @@ int platform_default_i(const char *name, int def) { return def; }
 FontSpec *platform_default_fontspec(const char *name) { return fontspec_new(""); }
 Filename *platform_default_filename(const char *name) { return filename_from_str(""); }
 char *x_get_default(const char *key) { return NULL; }
-void log_eventlog(void *handle, const char *event) {}
+void log_eventlog(LogContext *logctx, const char *event) {}
 int from_backend(void *frontend, int is_stderr, const void *data, int datalen)
 { assert(!"only here to satisfy notional call from backend_socket_log"); }
 

unix/uxplink.c

@@ -25,7 +25,7 @@
 
 #define MAX_STDIN_BACKLOG 4096
 
-static void *logctx;
+static LogContext *logctx;
 
 static struct termios orig_termios;
 

unix/uxpty.c

@@ -1212,7 +1212,7 @@ static void pty_provide_ldisc(void *handle, Ldisc *ldisc)
     /* This is a stub. */
 }
 
-static void pty_provide_logctx(void *handle, void *logctx)
+static void pty_provide_logctx(void *handle, LogContext *logctx)
 {
     /* Pty pty = (Pty)handle; */
     /* This is a stub. */

unix/uxser.c

@@ -549,7 +549,7 @@ static void serial_provide_ldisc(void *handle, Ldisc *ldisc)
     /* This is a stub. */
 }
 
-static void serial_provide_logctx(void *handle, void *logctx)
+static void serial_provide_logctx(void *handle, LogContext *logctx)
 {
     /* This is a stub. */
 }