Don't assume someone else pulls in errno.h
Summary:
This fixes compile error on FreeBSD 11:
[ 5%] Building CXX object src/CMakeFiles/kaffeine.dir/dvb/dvbrecording.cpp.o
/home/adridg/src/kde/kaffeine/src/dvb/dvbrecording.cpp:817:86: error: use of
undeclared identifier 'errno' ..."Cannot open file %s. Error: %d", qPrintable(file.fileName()), errno);
Reviewers: mauroc, pino
Reviewed By: mauroc, pino
Differential Revision: https://phabricator.kde.org/D17735