switch io_fds from array to newly implemented (hopefully thread-safe) iarray

switch epoll from level triggering to edge triggering

buffer/buffer_mmapread.c

@@ -6,7 +6,7 @@ static ssize_t op() {
 }
 
 int buffer_mmapread(buffer* b,const char* filename) {
-  if (!(b->x=mmap_read(filename,&b->n))) return -1;
+  if (!(b->x=(char*)mmap_read(filename,&b->n))) return -1;
   b->p=0; b->a=b->n;
   b->fd=-1;
   b->op=op;