Add fixed-size, preallocated pool support

Simply call pool_init_fixed(...) before using the pool. Note that
fixed, preallocated pools live in individually-mmap'ed address
segments, except for the free element bitmap. A large fixed pool can
exceed 4gb.

Fix tcp buffer allocator leak, remove broken assert

Change-Id: I4421082e12a77c41c6e20f7747f3150dcd01fc26
Signed-off-by: Dave Barach <dave@barachs.net>
diff --git a/src/svm/svm_fifo_segment.c b/src/svm/svm_fifo_segment.c
index 6600a42..97d9976 100644
--- a/src/svm/svm_fifo_segment.c
+++ b/src/svm/svm_fifo_segment.c
@@ -461,7 +461,7 @@
 
   freelist_index = f->freelist_index;
 
-  ASSERT (freelist_index > 0 && freelist_index < vec_len (fsh->free_fifos));
+  ASSERT (freelist_index < vec_len (fsh->free_fifos));
 
   ssvm_lock_non_recursive (sh, 2);
   oldheap = ssvm_push_heap (sh);