gallium: Deprecate GETENV. Replace by debug_get_bool_option.

debug_get_bool_option will interpret "n", "no", "0", "f", or
"false" as FALSE; and everything else as TRUE. The default value
(used when the variable is not set) is received as a parameter.

src/gallium/include/pipe/p_util.h

@@ -140,8 +140,6 @@ REALLOC( void *old_ptr, unsigned old_size, unsigned new_size )
 
 #define CALLOC_STRUCT(T)   (struct T *) CALLOC(1, sizeof(struct T))
 
-#define GETENV( X ) debug_get_option( X, NULL )
-
 
 /**
  * Return memory on given byte alignment