Move class auto_buffer to separate file
auto_buffer: add doxy, small refactoring for clarity and optimization
[win32] PlatformDefs: use typedef for 'ssize_t', define SSIZE_MAX
CFile::LoadFile: use ssize_t return type, check for negative value; update types in CFile::Copy()
Remove FileUtils::LoadFile() function and replace it usage with CFile::LoadFile()
Update code to check for negative return values of "CFile::LoadFile()"
JpegIO::Open: replace moved code with function call
WindowXML::LoadXML: replace broken file loading with native implementation
ModplugCodec::Init: replace unchecked file loading with "LoadFile()"
GUIDialogAddonInfo::OnJobComplete: replace unchecked file loading with "LoadFile()"
CNfoFile: replace unchecked file loading with "LoadFile()", replace char* buffer with std::string
CPODocument::LoadFile: replace file loading with "LoadFile()"
MusicDatabase::ImportKaraokeInfo: replace file loading with "LoadFile()"
KaraokeLyricsCDG::Load: load file by 'LoadFile()'
KaraokeLyricsTextUStar::readFile: replace file loading with "LoadFile()"
KaraokeLyricsTextLRC::Load: replace file loading with "LoadFile()"
KaraokeLyricsTextKAR: replace file loading with "LoadFile()", use auto_buffer for m_midiData
Merge pull request #4961 from Karlson2k/FileLoad_use_01

Use File::LoadFile() instead of custom implementaions