avisynth: Use RTLD_LOCAL instead of RTLD_GLOBAL

There shouldn't be any need to add the loaded libraries to the global
symbol namespace.
Signed-off-by: NMartin Storsjö <martin@martin.st>

libavformat/avisynth.c

@@ -52,7 +52,7 @@
       #define AVISYNTH_LIB "libavxsynth.so"
     #endif
 
-  #define LoadLibrary(x) dlopen(x, RTLD_NOW | RTLD_GLOBAL)
+  #define LoadLibrary(x) dlopen(x, RTLD_NOW | RTLD_LOCAL)
   #define GetProcAddress dlsym
   #define FreeLibrary dlclose
 #endif