Add missing descriptions for several libraries to build.conf. These descriptions are used in pkg-config .pc files and I noticed a few .pc files were lacking them.
Add missing descriptions for several libraries to build.conf.
These descriptions are used in pkg-config .pc files and I noticed
a few .pc files were lacking them.

* build.conf
  (libsvn_fs_base, libsvn_fs_fs, libsvn_fs_x,
   libsvn_fs_util, libsvn_ra, libsvn_ra_serf,
   libsvn_ra_svn, libsvn_ra_local): Describe these libraries.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1574720 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion