log1pl-ieee: Work around test failure on IRIX 6.5. * m4/log1pl-ieee.m4: New file. * m4/log1pl.m4 (gl_FUNC_LOG1PL): If gl_FUNC_LOG1PL_IEEE is present, test whether log1pl works with a minus zero argument. Replace it if not. * lib/math.in.h (log1pl): Override if REPLACE_LOG1PL is 1. * m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize REPLACE_LOG1PL. * modules/math (Makefile.am): Substitute REPLACE_LOG1PL. * modules/log1pl (configure.ac): Consider REPLACE_LOG1PL. (Depends-on): Update conditions. * modules/log1pl-ieee (Files): Add m4/log1p-ieee.m4, m4/minus-zero.m4, m4/signbit.m4. (configure.ac): Invoke gl_FUNC_LOG1PL_IEEE. * doc/posix-functions/log1pl.texi: Mention the log1pl-ieee module.

new file mode 100644
--- /dev/null
+++ b/m4/log1pl-ieee.m4
@@ -0,0 +1,15 @@
+# log1pl-ieee.m4 serial 1
+dnl Copyright (C) 2012 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl This macro is in a separate file (not in remainder.m4 and not inlined in the
+dnl module description), so that gl_FUNC_LOG1PL can test whether 'aclocal' has
+dnl found uses of this macro.
+
+AC_DEFUN([gl_FUNC_LOG1PL_IEEE],
+[
+  m4_divert_text([INIT_PREPARE], [gl_log1pl_required=ieee])
+  AC_REQUIRE([gl_FUNC_LOG1PL])
+])