math: Ensure declarations of math functions. * modules/acosf (Depends-on): Add 'extensions'. * modules/asinf (Depends-on): Likewise. * modules/atan2f (Depends-on): Likewise. * modules/atanf (Depends-on): Likewise. * modules/cbrt (Depends-on): Likewise. * modules/cbrtf (Depends-on): Likewise. * modules/cbrtl (Depends-on): Likewise. * modules/copysignf (Depends-on): Likewise. * modules/copysignl (Depends-on): Likewise. * modules/cosf (Depends-on): Likewise. * modules/coshf (Depends-on): Likewise. * modules/expf (Depends-on): Likewise. * modules/fabsf (Depends-on): Likewise. * modules/fabsl (Depends-on): Likewise. * modules/fmaf (Depends-on): Likewise. * modules/fmal (Depends-on): Likewise. * modules/fmodf (Depends-on): Likewise. * modules/fmodl (Depends-on): Likewise. * modules/frexpf (Depends-on): Likewise. * modules/frexpl (Depends-on): Likewise. * modules/hypot (Depends-on): Likewise. * modules/hypotf (Depends-on): Likewise. * modules/hypotl (Depends-on): Likewise. * modules/ldexpf (Depends-on): Likewise. * modules/ldexpl (Depends-on): Likewise. * modules/log10f (Depends-on): Likewise. * modules/log10l (Depends-on): Likewise. * modules/log1p (Depends-on): Likewise. * modules/logb (Depends-on): Likewise. * modules/logf (Depends-on): Likewise. * modules/modff (Depends-on): Likewise. * modules/modfl (Depends-on): Likewise. * modules/powf (Depends-on): Likewise. * modules/remainderf (Depends-on): Likewise. * modules/remainderl (Depends-on): Likewise. * modules/rintf (Depends-on): Likewise. * modules/rintl (Depends-on): Likewise. * modules/sinf (Depends-on): Likewise. * modules/sinhf (Depends-on): Likewise. * modules/sqrtf (Depends-on): Likewise. * modules/tanf (Depends-on): Likewise. * modules/tanhf (Depends-on): Likewise. * m4/acosf.m4 (gl_FUNC_ACOSF): Require gl_USE_SYSTEM_EXTENSIONS. * m4/asinf.m4 (gl_FUNC_ASINF): Likewise. * m4/atan2f.m4 (gl_FUNC_ATAN2F): Likewise. * m4/atanf.m4 (gl_FUNC_ATANF): Likewise. * m4/cbrt.m4 (gl_FUNC_CBRT): Likewise. * m4/cbrtf.m4 (gl_FUNC_CBRTF): Likewise. * m4/cbrtl.m4 (gl_FUNC_CBRTL): Likewise. * m4/copysignf.m4 (gl_FUNC_COPYSIGNF): Likewise. * m4/copysignl.m4 (gl_FUNC_COPYSIGNL): Likewise. * m4/cosf.m4 (gl_FUNC_COSF): Likewise. * m4/coshf.m4 (gl_FUNC_COSHF): Likewise. * m4/expf.m4 (gl_FUNC_EXPF): Likewise. * m4/fabsf.m4 (gl_FUNC_FABSF): Likewise. * m4/fabsl.m4 (gl_FUNC_FABSL): Likewise. * m4/fmaf.m4 (gl_FUNC_FMAF): Likewise. * m4/fmal.m4 (gl_FUNC_FMAL): Likewise. * m4/fmodf.m4 (gl_FUNC_FMODF): Likewise. * m4/fmodl.m4 (gl_FUNC_FMODL): Likewise. * m4/frexpf.m4 (gl_FUNC_FREXPF): Likewise. * m4/frexpl.m4 (gl_FUNC_FREXPL): Likewise. * m4/hypot.m4 (gl_FUNC_HYPOT): Likewise. * m4/hypotf.m4 (gl_FUNC_HYPOTF): Likewise. * m4/hypotl.m4 (gl_FUNC_HYPOTL): Likewise. * m4/ldexpf.m4 (gl_FUNC_LDEXPF): Likewise. * m4/ldexpl.m4 (gl_FUNC_LDEXPL): Likewise. * m4/log10f.m4 (gl_FUNC_LOG10F): Likewise. * m4/log10l.m4 (gl_FUNC_LOF10L): Likewise. * m4/logb.m4 (gl_FUNC_LOGB): Likewise. * m4/logf.m4 (gl_FUNC_LOGF): Likewise. * m4/modff.m4 (gl_FUNC_MODFF): Likewise. * m4/modfl.m4 (gl_FUNC_MODFL): Likewise. * m4/powf.m4 (gl_FUNC_POWF): Likewise. * m4/remainderf.m4 (gl_FUNC_REMAINDERF): Likewise. * m4/remainderl.m4 (gl_FUNC_REMAINDERL): Likewise. * m4/rintf.m4 (gl_FUNC_RINTF): Likewise. * m4/rintl.m4 (gl_FUNC_RINTL): Likewise. * m4/sinf.m4 (gl_FUNC_SINF): Likewise. * m4/sinhf.m4 (gl_FUNC_SINHF): Likewise. * m4/sqrtf.m4 (gl_FUNC_SQRTF): Likewise. * m4/tanf.m4 (gl_FUNC_TANF): Likewise. * m4/tanhf.m4 (gl_FUNC_TANHF): Likewise.

--- a/m4/logf.m4
+++ b/m4/logf.m4
@@ -1,4 +1,4 @@
-# logf.m4 serial 1
+# logf.m4 serial 2
 dnl Copyright (C) 2011-2012 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -9,6 +9,9 @@
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_LOG])
 
+  dnl Persuade glibc <math.h> to declare logf().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
   dnl Test whether logf() exists. Assume that logf(), if it exists, is
   dnl defined in the same library as log().
   save_LIBS="$LIBS"