Initial modifications for XML-based sheet readers to use XMLReader via streaming for large files in the listWorksheetNames() and listWorksheetInfo() methods... still needs some additional work for merged cells to work correctly, but gives a hell of a memory boost and executes more quickly - the same principles will be applied to the core data readers, but that still requires a lot more work. However, when completed, the effort should be worth it for both speed and memory usage, and the code should be a lot cleaner for the core data reader as well
Modify listWorksheetNames() and listWorksheetInfo to use XMLReader with streamed XML rather than SimpleXML
General: (dbonsch) Work item GH-78 - Restructuring of PHPExcel Exceptions
Set correct active sheet when setReadDataOnly(true) and only loading a selection of two or more worksheets rather than all worksheets
added the actual number of sheets in the out of bounds exception
added the requested index to the out of bounds exception
Still improving the out of bounds error messages in the exceptions.
minor architecture improvement
  - used strtoupper to get rid of case sensitive name checks
  - added "else if", it's not nessecary to check for the second "if", if
the first one was allready true
Improved the phrasing of the error messages.
replaced tabs by 4 spaces
replaced tabs by 4 spaces
reformated the docblock comments (looked a litle strange after
replacing the tabs)
replaced tabs by 4 spaces
#131 added a check if the constant IDENTIFIER_OLE allready exists,
thx to @prolic
Merge branch 'develop' into experimental
Bugfix: Work item GH-130 - Single cell print area
Merge branch 'develop' of https://github.com/PHPOffice/PHPExcel into develop
fix typo in phpdoc
fix typo in phpdoc
Merge pull request #135 from nicoder/patch-1

fix typo in phpdoc