hypot-ieee: Work around test failure on OSF/1 and native Windows. * lib/math.in.h (hypot): New declaration. * lib/hypot.c: New file. * m4/hypot-ieee.m4: New file. * m4/hypot.m4 (gl_FUNC_HYPOT): If gl_FUNC_HYPOT_IEEE is present, test whether hypot works with mixed NaN and Infinity arguments. Replace it if not. * m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize GNULIB_HYPOT, REPLACE_HYPOT. * modules/math (Makefile.am): Substitute GNULIB_HYPOT, REPLACE_HYPOT. * modules/hypot (Files): Add lib/hypot.c. (Depends-on): Add dependencies. (configure.ac): Arrange to compile replacement if REPLACE_HYPOT is 1. * modules/hypot-ieee (Files): Add m4/hypot-ieee.m4. (configure.ac): Invoke gl_FUNC_HYPOT_IEEE. * tests/test-math-c++.cc: Check the declaration of hypot. * doc/posix-functions/hypot.texi: Mention the hypot-ieee module.

--- a/tests/test-math-c++.cc
+++ b/tests/test-math-c++.cc
@@ -158,7 +158,9 @@
 #if GNULIB_TEST_HYPOTF
 SIGNATURE_CHECK (GNULIB_NAMESPACE::hypotf, float, (float, float));
 #endif
-//SIGNATURE_CHECK (GNULIB_NAMESPACE::hypot, double, (double, double));
+#if GNULIB_TEST_HYPOT
+SIGNATURE_CHECK (GNULIB_NAMESPACE::hypot, double, (double, double));
+#endif
 #if GNULIB_TEST_HYPOTL
 SIGNATURE_CHECK (GNULIB_NAMESPACE::hypotl, long double,
                  (long double, long double));