acinclude.m4: CHECK_MATH_DECL_AND_LINKAGE for hypot, hypotf, hypotl, atan2f, atan2l.

        * acinclude.m4: CHECK_MATH_DECL_AND_LINKAGE for hypot, hypotf,
        hypotl, atan2f, atan2l.  Remove from REPLACE_MATHFUNCS list.
        * aclocal.m4: Regenerate.
        * config.h.in: Likewise.
        * configure: Likewise.
        * libmath/Makefile.am (EXTRA_LONG_DOUBLE_yes): Remove hypotl.c
        (EXTRA_DIST): Remove hypot.c hypotf.c.
        * libmath/Makefile.am: Regenerate.
        * libmath/hypotf.c: Remove.
        * libmath/hypot.c: Likewise.
        * libmath/hypotl.c: Likewise.
        * libmath/stubs.c: The macros seen here are HAVE_xxx, not
        _GLIBCPP_HAVE_xxx.  Add long double versions.

From-SVN: r44334