function must not contain the package name component (for example,
function <code>Syscall</code> in package <code>syscall</code> should
use the name <code>·Syscall</code> instead of the equivalent name
<code>syscall·Syscall</code> in its <code>TEXT</code> directive).
For more complex situations, explicit annotation is needed.
These annotations use pseudo-instructions defined in the standard
<code>#include</code> file <code>funcdata.h</code>.