Improved performance

Bug #92 Large XML file without line breaks kills XML Copy Editor
Bug #136 Doesn't respect $CXXFLAGS for compilation$
Updated autoconf & automake files
Fixed a compiler warning: -Wreorder
Replaced wxFileName::DirExists with wxDirExists
Bug #185 Help file cannot be opened

Warn about invalid data paths
Fixed a problem when replacing '>' with '>>'

Other '>'s except the first one wouldn't be replaced.
Replaced wxFileName::FileExists with wxFileExists
Bug #145 When opening with xmlcopyeditor associated file when double-clicking on it opens twice
Fixed a compiler error for wxWidgets 2.8
Excluded windows related paths from being checked on Linux
Bug #156 Text encoding is changed in result file that occurs after computing of xpath
Use memory rather than temporary files to pass XML content
Replaced std::string with wxString
Bug #161 Validation of TEI Lite DTD fails

Don't treat validation warning as error
Prefer memory to temporary file
Use Xerces-C for DTD validation
Bug #159 Can't change encoding while "Save UTF-8 BOM" option selected