Sync final newlines

This patch adds some missing newlines and trims multiple newlines into
one.

According to POSIX, a line is a sequence of zero or more non-' <newline>'
characters plus a terminating '<newline>' character. [1] Files should
normally have at least one final newline character.

C89 [2] and later standards [3] mention a final newline:
"A source file that is not empty shall end in a new-line character,
which shall not be immediately preceded by a backslash character."

Although it is not mandatory for all files to have a final newline
fixed, a more consistent and homogeneous approach brings less of commit
differences issues and a better development experience in certain text
editors and IDEs.

[1] http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_206
[2] https://port70.net/~nsz/c/c89/c89-draft.html#2.1.1.2
[3] https://port70.net/~nsz/c/c99/n1256.html#5.1.1.2

tutorial/intro.md

@@ -28,4 +28,4 @@ This guide uses some terminology that you have to know. Don't worry, it's easy:
 
 ## Feedback
 Feedback is most certainly welcome on this document. Without your submissions and input, this document wouldn't exist.
-Please send your additions, comments and criticisms to the following email address: phpdoc@lists.php.net.
+Please send your additions, comments and criticisms to the following email address: phpdoc@lists.php.net.

tutorial/style.md

@@ -61,4 +61,4 @@ the [Foo Page][example]  | [click here][example], go [here][example]
 Unix                     | UNIX (it's a registered trademark)
 Windows                  | windows (when referring to Microsoft Windows)
 
-[example]: http://example.com
+[example]: http://example.com