doc: xss_clean() method is in Security, not Input

The Input doc does talk about xss filtering, but they refer you to Security for details, which is where the function is actually defined.  It gives more detail about what the function is supposed to do, and avoids some irrelevance.

It's probably not a big deal; it just looks wrong.  It _might_ have been responsible for [confusion](http://stackoverflow.com/questions/13570522/this-input-xss-cleandata-giving-fatal-error-with-codeigniter) sometimes.
[ci skip] Minor style/spacing changes following PR #2087
issue #2092 : Improve/Revise JS and CSS minify method
issue #2092 : Improve/Revise JS and CSS minify method
issue #2092 : Improve/Revise JS and CSS minify method
issue #2092 : Improve/Revise JS and CSS minify method (code refinements)
issue #2092 : code refinements
Merge pull request #2097 from AndrewPodner/feature-minify

issue #2092 : Improve/Revise JS and CSS minify method
Merge branch 'develop' of github.com:EllisLab/CodeIgniter into develop
Minor improvements to the Output class
Update CI_Output::get_header() test
Improved extensibility of the URI class by modifying `_uri_assoc()` to (1) not force a specific list of valid options for `$which`, and (2) build the `$segment_array` and `$total_segments` dynamically regardless of the contents of `$which`.

Signed-off-by: Daniel Hunsaker <danhunsaker@gmail.com>
Fixed normalization of headers under Apache

The existing header normalization routine converts headers provided by Apache (that is, with `-` in the name instead of `_`)
to all lowercase, with the exception of the first character.  This is different from the expected result, wherein each word
of the header is capitalized.  For example, `CONTENT-LENGTH` would normalize to `Content-length` instead of the expected
`Content-Length`.  The reason for this is that the existing code is only converting underscores to spaces, and leaving hyphens
untouched.  The fix is to replace hyphens with spaces as well before passing the result through `ucwords()`.

That fix is included here.

Signed-off-by: Daniel Hunsaker <danhunsaker@gmail.com>
Merge pull request #2107 from danhunsaker/feature/header-normalization

Fixed normalization of headers under Apache
[ci skip] Happy new year
Merge pull request #2106 from danhunsaker/feature/uri-extensibility

Improved extensibility of the URI class
Fix #2108
doc: fix table markup in previous commit

"These "border lines" need to have a length higher or equal to the
longest line in the table that would be generated, so you'll have
to update them as well." - narfbg
Merge pull request #2075 from sourcejedi/patch-1

doc: xss_clean() method is in Security, not Input
fix a typo in index.php