bootloader: Make releasing the heap the platform loader's responsibility.

Otherwise, platform loaders couldn't make heap allocations inside
platform_start_kernel(), which some loaders (e.g. EFI) do.

Implement calling heap_release() for the BIOS loaders at least.
This gets us back the ~1.5MB of bootloader heap memory there.

headers/private/kernel/boot/heap.h

@@ -1,23 +1,28 @@
 /*
-** Copyright 2003, Axel Dörfler, [email protected]. All rights reserved.
-** Distributed under the terms of the MIT License.
-*/
+ * Copyright 2003, Axel Dörfler, [email protected]. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ */
 #ifndef KERNEL_BOOT_HEAP_H
 #define KERNEL_BOOT_HEAP_H
 
+
 #include <SupportDefs.h>
 #include <boot/stage2_args.h>
 
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-extern void heap_release(struct stage2_args *args);
-extern void heap_print_statistics();
+
 extern status_t heap_init(struct stage2_args *args);
+extern void heap_print_statistics();
+extern void heap_release();
+
 
 #ifdef __cplusplus
 }
 #endif
 
+
 #endif	/* KERNEL_BOOT_HEAP_H */