Cleanup and enhance top-level INSTALL file for release:

- add at least one typical example to give
  the user an impression how to use the configure script

- add contact informations to give the user
  the next logical step after installation

- add four important notes to make the usage of
  --enable-shared more clear to the user

- fix indentation


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80905 13f79535-47bb-0310-9956-ffa450edef68