Remove mmap_unaligned.

Remove mmap_unaligned, which was used to heuristically decide whether to
optimistically call mmap() in such a way that could reduce the total
number of system calls.  If I remember correctly, the intention of
mmap_unaligned was to avoid always executing the slow path in the
presence of ASLR.  However, that reasoning seems to have been based on a
flawed understanding of how ASLR actually works.  Although ASLR
apparently causes mmap() to ignore address requests, it does not cause
total placement randomness, so there is a reasonable expectation that
iterative mmap() calls will start returning chunk-aligned mappings once
the first chunk has been properly aligned.

src/chunk.c

@@ -274,7 +274,7 @@ chunk_dealloc(void *chunk, size_t size, bool unmap)
 }
 
 bool
-chunk_boot0(void)
+chunk_boot(void)
 {
 
 	/* Set variables according to the value of opt_lg_chunk. */
@@ -301,13 +301,3 @@ chunk_boot0(void)
 
 	return (false);
 }
-
-bool
-chunk_boot1(void)
-{
-
-	if (chunk_mmap_boot())
-		return (true);
-
-	return (false);
-}