missing autoheader bits

[Benjamin Kosnik]

Kelley: this is fallout from your recent change(s).

% aclocal; autoconf; autoheader 

gives:

autoheader: warning: missing template: HAVE_ATAN2F
autoheader: Use AC_DEFINE([HAVE_ATAN2F], [], [Description])
autoheader: warning: missing template: HAVE_ATAN2L
autoheader: warning: missing template: HAVE_COPYSIGNF
autoheader: warning: missing template: HAVE_HYPOT
autoheader: warning: missing template: HAVE_MODFF
autoheader: warning: missing template: HAVE_MODFL

-benjamin