reviewed use of multiple-choice attributes and definition of “unix” (see conditions)

uniform style of notes and new feature markers

- stripped trailing whitespace;
- corrected the tag soup;
- corrected Java versions (1.4 followed by 5);
- stripped inline styling (use CSS for uniformity).

Only the manual will be in the distribution


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@1084809 13f79535-47bb-0310-9956-ffa450edef68