Support ELF64 in the kernel.

This has been done by adding typedefs in elf_common.h to the correct ELF
structures for the architecture, and changing all Elf32_* uses to those
types. I don't know whether image loading works as I cannot test it yet,
there may be some 64-bit safety issues around. However, symbol lookup for
the kernel is working correctly.

headers/private/kernel/boot/elf.h

@@ -77,6 +77,14 @@ struct preloaded_elf64_image : public preloaded_image {
 	FixedWidthPointer<Elf64_Sym> debug_symbols;
 } _PACKED;
 
+
+#if B_HAIKU_64_BIT
+typedef preloaded_elf64_image preloaded_elf_image;
+#else
+typedef preloaded_elf32_image preloaded_elf_image;
+#endif
+
+
 #ifdef _BOOT_MODE
 extern status_t boot_elf_resolve_symbol(preloaded_elf32_image* image,
 	struct Elf32_Sym* symbol, Elf32_Addr* symbolAddress);