The find module for QScintilla included with sqlitebrowser has never worked
(well) on FreeBSD. Then the port used en embedded copy of QScintilla.
Switch to using the system QScintilla.

This change is triggered by CMake 3.11, which tried to build the embedded
QScintilla slightly differently. That fails because there are header
files declaring enum { SCI_CANREDO = 2016 } *and also* header files
that #define SCI_CANREDO 2016; the include order is very fragile.

Also reported upstream.

Reviewed by: lbartoletti_tuxfamily (maintainer)
Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D14930