paper: preserve whitespace on description instead of adding breaks

This preserves the indentation of text in the changeset description.

This is useful for example for descriptions containing command line
use case examples like:

  $ hg -q heads
  13934:648a834cca14
  13912:71ea5b2b9517

Without this patch, such space-char indented text was just left aligned.

mercurial/templates/paper/changeset.tmpl

@@ -40,7 +40,7 b''
 files, or words in the commit message</div>
 </form>
 
-<div class="description">{desc|strip|escape|addbreaks|nonempty}</div>
+<div class="description">{desc|strip|escape|nonempty}</div>
 
 <table id="changesetEntry">
 <tr>

mercurial/templates/static/style-paper.css

@@ -210,6 +210,7 b' div.description {'
   border-left: 2px solid #999;
   margin: 1em 0 1em 0;
   padding: .3em;
+  white-space: pre;
 }
 
 /* Graph */