update version to 9.5.6

updated version to 9.5.4

  BUILDING NOTICE makefiles/Mf-install.in makefiles/Makefile-csug.in
  scheme.1.in c/Makefile.a6nt c/Makefile.i3nt c/Makefile.ta6nt
  c/Makefile.ti3nt mats/Mf-a6nt mats/Mf-i3nt mats/Mf-ta6nt
  mats/Mf-ti3nt workarea c/scheme.rc s/7.ss s/cmacros.ss
  release_notes/release_notes.stex csug/copyright.stex csug/csug.stex
  bintar/Makefile rpm/Makefile pkg/Makefile wininstall/Makefile
  wininstall/a6nt.wxs wininstall/i3nt.wxs wininstall/ta6nt.wxs
  wininstall/ti3nt.wxs

missed one change in bintar/Makefile

  newrelease
  bintar/Makefile

Start on release notes.

- added library-search-handler, compile-whole-library, and improved
  packaging to the release notes.
    release_notes/release_notes.stex

- added version number to scheme.1.in trailer; updated date.

    scheme.1.in, newrelease
- removed version update of no-longer-existing bldnt.bat.  "fixed"
  sed patterns to replace \? with * for the benefit of the deficient
  mac sed.
    newrelease
- updated version to 9.5
    bintar BUILDING NOTICE makefiles/Mf-install.in scheme.1.in
    c/Makefile.i3nt c/Makefile.a6nt c/Makefile.ti3nt c/Makefile.ta6nt
    workarea c/scheme.rc s/7.ss s/cmacros.ss
    release_notes/release_notes.stex csug/csug.stex
- updated release notes and fixed user's guide overfull hbox.
    release-notes.stex, syntax.stex
- updated install target to do something more sensible
    release_notes/Makefile

updated release month to May

  release_notes.stex