problems with autoconf 2.59

[dstahlke]

Centos 5 has autoconf 2.59 and boost.m4 doesn't work there. The macros AC_PROG_GREP and AC_PROG_SED are not defined. If I remove those calls autoconf proceeds (albeit generating an invalid config file because GREP is not defined) but I get a warning:

configure:314: error: possibly undefined macro: BOOST_CPPFLAGS
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.
configure:314: error: possibly undefined macro: BOOST_ROOT