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.

include/jemalloc/internal/chunk.h

@@ -44,8 +44,7 @@ extern size_t		arena_maxclass; /* Max size class for arenas. */
 
 void	*chunk_alloc(size_t size, size_t alignment, bool base, bool *zero);
 void	chunk_dealloc(void *chunk, size_t size, bool unmap);
-bool	chunk_boot0(void);
-bool	chunk_boot1(void);
+bool	chunk_boot(void);
 
 #endif /* JEMALLOC_H_EXTERNS */
 /******************************************************************************/