Fix crash caused by infinite loop

When there is no data in the changeset table, Source_Date_Select()
goes into an infinite loop and crashes as PHP runs out of memory.
Github: fix broken link for Browse without SHA ref
Add 'Search' link to changesets list page
Add 'Back to Index' link to search results page
Do not interpret HTML tags in changeset messages

When displaying changesets, the commit message is now manually
transformed (adding href, bug and bugnote links + nl2br) instead of
calling string_display_links(), which avoids unwanted html tags
processing by the MantisCoreFormatting plugin.  Rationale: commit
messages being plain text, any html they may contain should not be
considered as formatting and must be displayed as-is.

Fixes #93
Fix HTML/CSS for account update form
Replace deprecated <acronym> element by <abbr>

Reference: http://www.w3.org/TR/html5/obsolete.html#acronym
Remove calls to helper_alternate_class()
HTML/CSS fixes for manage_config_page.php

Use a form-container div instead of table
HTML/CSS fixes for SourceSVN config

Use divs instead of table rows/cells
HTML/CSS fixes for index.php
Fix deprecated warning for db_get_table()
Fix PHP warning in search page
CSS improve layout with 'spacer' class for div
SVN: add title in update_config_form()
HTML/CSS fixes for search_page.php
HTML/CSS fixes for repo_manage_page.php
HTML/CSS fixes for search.php
New API to display pagination links

The new Source_View_Pagination() function removes redundant code from
the search and list pages, and improves it by

- using a closure instead of create_function()
- use MantisBT standard "first/prev/next/last" instead of "<</>>"
- print fewer page links, increasing the gap between them depending on
  total number of changesets (total / 10 rounded to nearest 10)
HTML/CSS fixes for list.php