add poppler source
Merge branch 'master' of https://github.com/Bramas/SimTex into plain_text_edit

Conflicts:
	source/mainwindow.cpp
	source/simtex.pro
	source/widgettextedit.cpp
	source/widgettextedit.h
Merge branch 'master' of https://github.com/Bramas/SimTex