Updated all cases of exit() to return a valid code

Specific codes are as follows, but can easily be changed if a different order/breakdown makes more sense:

- 0: Success; everything executed as planned
- 1: Configuration Error; something is wrong with/in the configuration file(s)
- 2: Class Not Found; what it says
- 3: Driver Method Unsupported; the method you're trying to use on a Driver doesn't exist
- 4: File Not Found; 404 error
- 5: Database Error; something is broken in the database somewhere
- 6: Invalid Input; the user attempted to submit a request with invlaid characters in 1+ key names
7 through 26 are reserved for future use
- 27: Generic Error; generated by show_error() when the status code is >= 100
28 through 127 are errors generated by user applications, normally by using show_error() with a status code below 100
128 through 254 should not be used by applications, as they are reserved by system-level functions
- 255: PHP Fatal Error; automatically generated by PHP for fatal errors, and therefore not allowed for our use

Status codes below 100 are shifted up by 28 to place them in the user error range.  It may make more sense to have these codes
left alone and instead shift the CI errors into the 101 through 127 space, but that's not what I opted for here.

It would probably also be a good idea to replace the hard-coded numbers with constants or some such, but I was in a bit of a
hurry when I made these changes, so I didn't look around for the best place to do this.  With proper guidance, I could
easily amend this commit with another that uses such constant values.

Signed-off-by: Daniel Hunsaker <danhunsaker@gmail.com>
Added small feature to profiler: total execution time count

adds additional information to profiler like:
DATABASE:  test   QUERIES: 3 (0.0016s)  (Hide)
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
changes according to narfbg's request
changes according to narfbg's request
Update system/core/Common.php

Updated is_https() to avoid "NULL" or "0" values to set HTTPS.
Merge pull request #2241 from TimHas/develop

Added small feature to profiler: total execution time count
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
Various cosmetic fixes
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.