qemu-log: cleanup

Don't use global variables directly but via accessor functions. Rename globals.

Convert macros to functions, add GCC format attributes.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

linux-user/main.c

@@ -1306,8 +1306,9 @@ do {                                                                    \
     fprintf(stderr, fmt , ## __VA_ARGS__);                              \
     cpu_dump_state(env, stderr, fprintf, 0);                            \
     qemu_log(fmt, ## __VA_ARGS__);                                      \
-    if (logfile)                                                        \
+    if (qemu_log_enabled()) {                                           \
         log_cpu_state(env, 0);                                          \
+    }                                                                   \
 } while (0)
 
 static int do_store_exclusive(CPUPPCState *env)