Update system/core/Log.php

Updated Log.php so that a developer can extend it and change the log file extension.

It makes sense to default to .php when logs are in the public web folder.  It would be nice if a developer moves the log file path we have the option to use a standard extension like .log
Added support for changing the default log file extension from .php to whatever is preferred. example (.log)

This is a follow up to this pull request.

https://github.com/EllisLab/CodeIgniter/pull/2243
Update system/core/Common.php

Updated is_https() to avoid "NULL" or "0" values to set HTTPS.
Update system/core/Log.php

Added ltrim() as requested to strip '.' incase it's added by mistake.
Update system/core/Log.php

Don't print no script access code into log file if log file is not .php anymore.
Update system/core/Common.php
Update system/core/Common.php
Merge pull request #2248 from vlakoff/develop

Various cosmetic fixes
Update system/core/Log.php

Added a space after the comma on the ltrim().
Update system/core/Common.php

If using nginx instead of apache by default nginx will not populate the $_SERVER['HTTPS'] value.  This change allows falling back to checking the port number of the request to determine if your on SSL or not.

The other option is adding the following to your nginx config.

fastcgi_param HTTPS on; #some php apps require this to detent https
Revert "Update system/core/Common.php"

This reverts commit 8af05ac97513764cc539919e179794df87352c30.
Revert "Revert "Update system/core/Common.php""

This reverts commit 3de57eaea8510ea9cfd70f063565c24904669c4c.
Revert "Update system/core/Log.php"

This reverts commit bbc6ab4736a896be83e3e3d5f8856374ffa2984c.
Revert "Update system/core/Common.php"

This reverts commit 8af05ac97513764cc539919e179794df87352c30.
Merge pull request #2243 from chrispassas/develop

Update system/core/Log.php
Merge pull request #2245 from maltzurra/patch-1

Fixed is_https() to avoid incorrect detection.
Fix some stuff from recent pull requests
Fix #2247
Added keep-alive connection to SMTP. Fixed socket read/write timeouts. Added PHP useragent
Fixed form helper variable error

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>