Updated in accordance with feedback from @narfbg

- Removed commented lists of constants from the three reference conventions,
  replacing each with the URLs at which more information can be found.
- Renamed a few constants to more closely reflect CodeIgniter conventions.
- Modified a couple of lines which were in violation of the CI Style Guide.

Signed-off-by: Daniel Hunsaker <danhunsaker@gmail.com>
diff --git a/application/config/constants.php b/application/config/constants.php
index 32a7159..dc84712 100644
--- a/application/config/constants.php
+++ b/application/config/constants.php
@@ -80,104 +80,30 @@
 |
 | Used to indicate the conditions under which the script is exit()ing.
 | While there is no universal standard for error codes, there are some
-| broad conventions.  Three such conventions are presented below, for
+| broad conventions.  Three such conventions are mentioned below, for
 | those who wish to make use of them.  The CodeIgniter defaults were 
 | chosen for the least overlap with these conventions, while still
 | leaving room for others to be defined in future versions and user
-| applications.  The CodeIgniter values are defined last so you can 
-| set them to values used by any of the other conventions, and do so 
-| by name instead of value.
+| applications.
+| 
+| The three main conventions used for determining exit status codes
+| are as follows:
+|
+|    Standard C/C++ Library (stdlibc):
+|       http://www.gnu.org/software/libc/manual/html_node/Exit-Status.html
+|       (This link also contains other GNU-specific conventions)
+|    BSD sysexits.h:
+|       http://www.gsp.com/cgi-bin/man.cgi?section=3&topic=sysexits
+|    Bash scripting:
+|       http://tldp.org/LDP/abs/html/exitcodes.html
 |
 */
-
-/*
- * standard C/C++ library (stdlibc):
- */
-/*
-define('LIBC_EXIT_SUCCESS', 0);
-define('LIBC_EXIT_FAILURE', 1); // generic errors
-*/
-
-/* 
- * BSD sysexits.h 
- */
-/*
-define('SYS_EX_OK', 0); // successful termination
-define('SYS_EX_USAGE', 64); // command line usage error
-define('SYS_EX_DATAERR', 65); // data format error
-define('SYS_EX_NOINPUT', 66); // cannot open input
-define('SYS_EX_NOUSER', 67); // specified user unknown
-define('SYS_EX_NOHOST', 68); // specified host name unknown
-define('SYS_EX_UNAVAILABLE', 69); // service unavailable
-define('SYS_EX_SOFTWARE', 70); // internal software error
-define('SYS_EX_OSERR', 71); // system error (e.g., can't fork)
-define('SYS_EX_OSFILE', 72); // critical OS file missing
-define('SYS_EX_CANTCREAT', 73); // can't create (user) output file
-define('SYS_EX_IOERR', 74); // input/output error
-define('SYS_EX_TEMPFAIL', 75); // temporary failure; user is invited to retry
-define('SYS_EX_PROTOCOL', 76); // remote error in protocol
-define('SYS_EX_NOPERM', 77); // permission denied
-define('SYS_EX_CONFIG', 78); // configuration error
-*/
-
-/*
- * Bash scripting 
- */
-/*
-define('BASH_EXIT_SUCCESS', 0);
-define('BASH_EXIT_ERROR', 1);
-define('BASH_EXIT_BUILTIN_MISUSE', 2);
-define('BASH_EXIT_CANT_EXEC', 126);
-define('BASH_EXIT_CMD_NOT_FOUND', 127);
-define('BASH_EXIT_INVALID_EXIT', 128);
-define('BASH_EXIT_SIG_HUP', 129);
-define('BASH_EXIT_SIG_INT', 130);
-define('BASH_EXIT_SIG_QUIT', 131);
-define('BASH_EXIT_SIG_ILL', 132);
-define('BASH_EXIT_SIG_TRAP', 133);
-define('BASH_EXIT_SIG_ABRT', 134);
-define('BASH_EXIT_SIG_BUS', 135);
-define('BASH_EXIT_SIG_FPE', 136);
-define('BASH_EXIT_SIG_KILL', 137);
-define('BASH_EXIT_SIG_USR1', 138);
-define('BASH_EXIT_SIG_SEGV', 139);
-define('BASH_EXIT_SIG_USR2', 140);
-define('BASH_EXIT_SIG_PIPE', 141);
-define('BASH_EXIT_SIG_ALRM', 142);
-define('BASH_EXIT_SIG_TERM', 143);
-define('BASH_EXIT_SIG_STKFLT', 144);
-define('BASH_EXIT_SIG_CHLD', 145);
-define('BASH_EXIT_SIG_CONT', 146);
-define('BASH_EXIT_SIG_STOP', 147);
-define('BASH_EXIT_SIG_TSTP', 148);
-define('BASH_EXIT_SIG_TTIN', 149);
-define('BASH_EXIT_SIG_TTOU', 150);
-define('BASH_EXIT_SIG_URG', 151);
-define('BASH_EXIT_SIG_XCPU', 152);
-define('BASH_EXIT_SIG_XFSZ', 153);
-define('BASH_EXIT_SIG_VTALRM', 154);
-define('BASH_EXIT_SIG_PROF', 155);
-define('BASH_EXIT_SIG_WINCH', 156);
-define('BASH_EXIT_SIG_IO', 157);
-define('BASH_EXIT_SIG_PWR', 158);
-define('BASH_EXIT_SIG_SYS', 159);
-*/
-/*
- * BASH_EXIT_OUTOFRANGE would be 255, and mean an exit status code beyond 
- * the range of 0-255 was given.  However, this code CANNOT BE USED IN PHP,
- * so it isn't actually defined, even in a comment.
- */
-
-/*
- * CodeIgniter defaults
- */
 define('EXIT_SUCCESS', 0); // no errors
-define('EXIT_FAILURE', 1); // generic error
+define('EXIT_ERROR', 1); // generic error
 define('EXIT_CONFIG', 3); // configuration error
-define('EXIT_404', 4); // file not found; convenience value
-define('EXIT_UNK_FILE', 4); // file not found
-define('EXIT_UNK_CLASS', 5); // unknown class
-define('EXIT_UNK_MEMBER', 6); // unknown class member
+define('EXIT_UNKNOWN_FILE', 4); // file not found
+define('EXIT_UNKNOWN_CLASS', 5); // unknown class
+define('EXIT_UNKNOWN_METHOD', 6); // unknown class member
 define('EXIT_USER_INPUT', 7); // invalid user input
 define('EXIT_DATABASE', 8); // database error
 define('EXIT__AUTO_MIN', 9); // lowest automatically-assigned error code