Fork as early as possible

If fork is requested, we fork as early as possible, way before anything
is initialized. This way, we don't need to do the gymnastics to make
OpenGL work properly across fork.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/options.h

@@ -17,7 +17,7 @@ typedef struct session session_t;
 /// Get config options that are needed to parse the rest of the options
 /// Return true if we should quit
 bool get_early_config(int argc, char *const *argv, char **config_file, bool *all_xerrors,
-                      int *exit_code);
+                      bool *fork, int *exit_code);
 
 /**
  * Process arguments and configuration files.