LibC: Run constructors on process startup.

Cooperate with the compiler to generate and execute the _init_array list
of constructor functions on userspace program statup. This took two days
to get working, my goodness. :^)

LibC/crti.S

@@ -0,0 +1,9 @@
+.global _init
+.section .init
+_init:
+    push %ebp
+
+.global _fini
+.section .fini
+_fini:
+    push %ebp