Enhancement: Enable `blank_line_after_opening_tag` fixer (#875)

Multiple micro-optimizations

* Replace `ob_get_contents();ob_clean()` with `ob_get_clean()`

`ob_get_clean()` is equivalent to `ob_get_contents()` followed by `ob_clean()`.

Multiple micro-optimizations

* Replace `ob_get_contents();ob_clean()` with `ob_get_clean()`

`ob_get_clean()` is equivalent to `ob_get_contents()` followed by `ob_clean()`.

* Replace `intval()` calls with `(int)` type cast

This is a micro-optimization because `intval()` is a function call, and the type cast is about 6 times fast.

* Replace `preg_replace` call that could be done with an `rtrim()` call

In `./error.php`, there is a `preg_replace('!/+$!', '', $URI);` call that essentially is equivalent to `rtrim()`, that both calls removing trailing slash characters in `$URI`.
The `rtim()` call is more legible and faster.

* Combine consecutive `str_replace` calls to a single `str_replace` call

* Use short ternary operator where possible

Improves code readability.

* Cascade various `else` statements where possible

Cleans up the code by removing unnecessary `else` blocks and moving the code to the parent context if the previous `if` block exits the function by either terminating the script, or with a `return` statement.

* Combine multiple `isset()` calls to a single `isset()`

`isset()` accepts multiple parameters and returns `true` only if all of the parameters are `isset`. It makes sense to combine multiple individual `isset` calls to a single call for better readability.

* Replace `for` loop with a `foreach` loop

* Remove unnecessary character escapes in regular expressions

Regular expression special characters are context-sensitive. For example, special characters such as `.` are not considered special within square braces (`[]`).
This removes several of such instances that certain characters are escaped, but it is not strictly necessary within the context. This improves the readability of the expression.

See more information at [PHP.Watch: Writing better Regular Expressions in PHP](https://php.watch/articles/php-regex-readability#reduce-escape)

* Remove unnecessary break statement

* Remove unnecessary PHP close tags

* Remove redundant JSON_ERROR_NONE check

Remove unnecessary `json_last_error() == JSON_ERROR_NONE` where the decoded object is inspected already.

Closes GH-603.

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Swap uses of _SERVER[DOCUMENT_ROOT] for __DIR__

2/4 - Update remaining except archives/ and release/.

Remove unused Git attributes ident

The $Id$ keywords were used in Subversion where they can be substituted
with filename, last revision number change, last changed date, and last
use

Remove unused Git attributes ident

The $Id$ keywords were used in Subversion where they can be substituted
with filename, last revision number change, last changed date, and last
user who changed it.

In Git this functionality is different and can be done with Git attribute
ident. These need to be defined manually for each file in the
.gitattributes file and are afterwards replaced with 40-character
hexadecimal blob object name which is based only on the particular file
contents.

This patch simplifies handling of $Id$ keywords by removing them since
they are not used anymore.

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Fix includes, and make redirects based on the already computed
language value

Get rid of some more stat() syscalls by avoiding include_path stats when
we know the exact relative path to the files

silence is_dir tests that may fail

hide the $MIRRORS array behind some access functions, for the most part

here goes nothing. the new php site look. let the torrent of
bitter and angry "i hate change" emails begin.

fix a couple of dumb typos to fix default language of manual on mirrors

bye, bye generated english manual. this should be exciting.