Log Message:
Update to 4.5.0. From the changelog:

- add note to README about problems with HP/UX prior to v.11.  Change code
  so that buffer still gets aligned even if you comment out the use of mlock()
  on such a platform.  Thanks: Keith Monahan.
- fix clear-buffer using incorrect param, causing spurious test failures.
  Thanks: Debin Dong.
- fix shell-ism in Makefile.  Thanks: Fabrice Fontaine.