CLHEP infrastructure improvements

CLHEP is a set of HEP-specific foundation and utility classes such as random number generators, physics vectors, and particle data tables. Although CLHEP has traditionally been distributed as one large library, the user community has long wanted the ability to build and use CLHEP packages separately. With the release of CLHEP 1.9, CLHEP has been reorganized and enhanced to enable building and using CLHEP packages individually as well as collectively. The revised build strategy employs all the components of the standard autotools suite: automake, autoconf, and libtool. In combination with the reorganization, the use of these components makes it easy not only to rebuild any single package (e.g., when that package changes), but also to add new packages.