fusee_cpp: validate mtc overlay before jumping to it.

mtc will jump back to us, so we need a compatible binary.

This also makes some changes to our layout to minimize the likelihood of
an incompatible mtc binary (I made some arbitrary .text/.rodata/.rwdata changes)
and saw identical mtc binaries, so hopefully this all works out.

fusee_cpp/program/program.ld

@@ -23,6 +23,9 @@ SECTIONS
         KEEP(*(.text._ZN3ams4util15GetMicroSecondsEv))
         KEEP(*(.text._ZN3ams4util16WaitMicroSecondsEi))
         KEEP(*(.text._ZN3ams6nxboot14ShowFatalErrorEPKcz))
+        KEEP(*(.text.memcpy))
+        KEEP(*(.text.memset))
+        KEEP(*(.text.memcmp))
         _*.o(SORT(.text*))
 		*(.text.unlikely .text.*_unlikely .text.unlikely.*)
 		*(.text.exit .text.exit.*)