* defines.h, rubysig.h, signal.c: removed macro handling which
  should be done in configure.

* configure.in (intrinsics.h): check if present.

* ruby.h: include intrinsics.h if available.

* bignum.c, marshal.c: include ieeefp.h if available.

* missing.h (isinf): define as a macro if finite() and isnan()
  are available.  [ruby-core:02032]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@5244 b2dd03c8-39d4-4d8f-98ff-823fe69b080e