[kernel] Run global constructors

Look up the global constructor list that the linker outputs, and run
them all. Required creation of the `kutil::no_construct` template for
objects that are constructed before the global constructors are run.

Also split the `memory_initialize` function into two - one for just
those objects that need to happen before the global ctors, and one
after.

Tags: memory c++

src/arch/x86_64/kernel.ld

@@ -20,6 +20,12 @@ SECTIONS
 		 *(.rodata)
 	}
 
+	.ctors : ALIGN(8) {
+		 __ctors = .;
+		 KEEP(*(.ctors))
+		 __ctors_end = .;
+	 }
+
 	.bss ALIGN(4096) : {
 		__bss_start = .;
 		*(.bss)