Add copyright info to libpng and libjpeg's GetLibraryVersionInfo(), fix libtiff's

[Blake-Madden]

Also adds lib name to PCRE's description to make it consistent with other libraries. Below are how the current descriptions appear:

Also, fixes libtiff's copyright. Currently, it looks like this:

"Copyright (c) 1988-1996 Sam LefflerCopyright (c) 1991-1996 Silicon Graphics, Inc."

Note the "LefflerCopyright". Newlines will now be preserved.

Also, use wxString::Trim instead of using pointer arithmetic that makes assumptions when getting libpng description.