cc for android: do not compile buffer.c and xfermem.c with NOXFERMEM

src/libout123/buffer.c

@@ -1,3 +1,4 @@
+#ifndef NOXFERMEM
 /*
 	buffer.c: output buffer
 
@@ -1016,3 +1017,4 @@ int buffer_loop(out123_handle *ao)
 		intflag = FALSE; /* Any possible harm by _not_ ensuring that the flag is cleared here? */
 	}
 }
+#endif

src/libout123/xfermem.c

@@ -1,3 +1,4 @@
+#ifndef NOXFERMEM
 /*
 	xfermem: unidirectional fast pipe
 
@@ -302,3 +303,4 @@ int INT123_xfermem_write(txfermem *xf, void *buffer, size_t bytes)
 	?	-1
 	:	0;
 }
+#endif