Fix the misunderstandings between local URL paths and local

system paths. Note that mod_rewrite handles _both_.
Fixed also some comments to make the explanations more clear.

PR: 12902
Obtained from: 2.1 (r1.144)
Reviewed by: Brad Nicholes, Will Rowe


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@99089 13f79535-47bb-0310-9956-ffa450edef68