container/index: initialise index_heap at load time

Fixes compiler diagnostic:

index.c:34:1: warning: no previous prototype for function
    'mowgli_index_init' [-Wmissing-prototypes]

src/libmowgli/container/index.c

@@ -19,6 +19,7 @@
  */
 
 #include "mowgli.h"
+#include "core/bootstrap_internal.h"
 
 struct mowgli_index_
 {
@@ -31,9 +32,10 @@ struct mowgli_index_
 static mowgli_heap_t *index_heap = NULL;
 
 void
-mowgli_index_init(void)
+mowgli_index_bootstrap(void)
 {
-	index_heap = mowgli_heap_create(sizeof(mowgli_index_t), 32, BH_NOW);
+	if (! (index_heap = mowgli_heap_create(sizeof(mowgli_index_t), 32, BH_NOW)))
+		abort();
 }
 
 mowgli_index_t *

src/libmowgli/core/bootstrap.c

@@ -47,6 +47,7 @@ MOWGLI_BOOTSTRAP_FUNC(mowgli_bootstrap_real)
 	mowgli_memslice_bootstrap();
 	mowgli_cacheline_bootstrap();
 	mowgli_interface_bootstrap();
+	mowgli_index_bootstrap();
 
 #ifdef _WIN32
 	mowgli_winsock_bootstrap();

src/libmowgli/core/bootstrap_internal.h

@@ -38,6 +38,7 @@ extern void mowgli_node_bootstrap(void);
 extern void mowgli_object_class_bootstrap(void);
 extern void mowgli_queue_bootstrap(void);
 extern void mowgli_random_bootstrap(void);
+extern void mowgli_index_bootstrap(void);
 
 #ifdef _WIN32
 extern void mowgli_winsock_bootstrap(void);