Move compat/ and bstr/ directory contents somewhere else

bstr.c doesn't really deserve its own directory, and compat had just
a few files, most of which may as well be in osdep. There isn't really
any justification for these extra directories, so get rid of them.

The compat/libav.h was empty - just delete it. We changed our approach
to API compatibility, and will likely not need it anymore.

options/m_config.h

@@ -22,7 +22,7 @@
 #include <stddef.h>
 #include <stdbool.h>
 
-#include "bstr/bstr.h"
+#include "misc/bstr.h"
 
 // m_config provides an API to manipulate the config variables in MPlayer.
 // It makes use of the Options API to provide a context stack that

options/m_option.h

@@ -23,7 +23,7 @@
 #include <stddef.h>
 #include <stdbool.h>
 
-#include "bstr/bstr.h"
+#include "misc/bstr.h"
 #include "audio/chmap.h"
 
 // m_option allows to parse, print and copy data of various types.

options/path.h

@@ -22,7 +22,7 @@
 #define MPLAYER_PATH_H
 
 #include <stdbool.h>
-#include "bstr/bstr.h"
+#include "misc/bstr.h"
 
 struct mpv_global;