RFC 1201 ammendment: naked functions are never inlined

clang will automatically set the NoInline attribute for naked functions
and the NoInline attribute wins over AlwaysInline attribute. Let's
follow their lead and specify the same requiremet.

As the compiller can't safely change/remove the prologue and epilogue
for naked functions when it inlines them inlining the naked functions
could result in strange bugs.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

text/1201-naked-fns.md

@@ -80,7 +80,8 @@ be aware of.
 # Detailed design
 
 Add a new function attribute to the language, `#[naked]`, indicating the
-function should have prologue/epilogue emission disabled.
+function should have prologue/epilogue emission disabled. Naked functions
+will never be inlined.
 
 Because the calling convention of a naked function is not guaranteed to match
 any calling convention the compiler is compatible with, calls to naked functions