MINOR: initcall: use initcalls for most post_{check,deinit} and per_thread*

Most calls to hap_register_post_check(), hap_register_post_deinit(),
hap_register_per_thread_init(), hap_register_per_thread_deinit() can
be done using initcalls and will not require a constructor anymore.
Let's create a set of simplified macros for this, called respectively
REGISTER_POST_CHECK, REGISTER_POST_DEINIT, REGISTER_PER_THREAD_INIT,
and REGISTER_PER_THREAD_DEINIT.

Some files were not modified because they wouldn't benefit from this
or because they conditionally register (e.g. the pollers).
diff --git a/src/chunk.c b/src/chunk.c
index 303d3fd..fa3fb71 100644
--- a/src/chunk.c
+++ b/src/chunk.c
@@ -92,10 +92,6 @@
 /* Initialize the trash buffers. It returns 0 if an error occurred. */
 int init_trash_buffers(int first)
 {
-	if (!first) {
-		hap_register_per_thread_init(init_trash_buffers_per_thread);
-		hap_register_per_thread_deinit(deinit_trash_buffers_per_thread);
-	}
 	pool_destroy(pool_head_trash);
 	pool_head_trash = create_pool("trash",
 				      sizeof(struct buffer) + global.tune.bufsize,
@@ -320,6 +316,9 @@
 	return diff;
 }
 
+REGISTER_PER_THREAD_INIT(init_trash_buffers_per_thread);
+REGISTER_PER_THREAD_DEINIT(deinit_trash_buffers_per_thread);
+
 /*
  * Local variables:
  *  c-indent-level: 8