#232 When compiling: "warning: inline function ‘sign’ declared but never defined"

[David Tonhofer]

Compiling XSB from scratch on Fedora 22 / gcc-5.1.1-4.fc22.x86_64

There seems to be an "extern inline int sign(Float);" in "cell_xsb.h"
that needs to be commented out; it is defined in "subp.c" and used there
only; this gets rid of "warning: inline function ‘sign’ declared but
never defined" warnings