Add support for text search across lines
Implemented in poppler MR: https://gitlab.freedesktop.org/poppler/poppler/merge_requests/267
As the new poppler result data type is PopplerFindRectangle, which incorporates more fields than just coordinates, we create a corresponding type in Evince, called EvFindRectangle, and use it all across Evince including the pdf backend (ev-poppler.cc) and djvu backend (djvu-document.c) which are the only backends that implement text search interface.
This new feature has the following aspects:
Ignores hyphen character while matching when 1) it's the last character of the line and 2) its corresponding matching character in the search term is not an hyphen too.
Any whitespace characters in the search term will be allowed to match on the logic position where the lines split (i.e. what would normally be the newline character in a text file, but PDF text does not include newline characters between lines).
It won't match on text spanning more than two lines, i.e. it only matches text spanning from end of one line to start of next line.
Part of issue #333