[4.2 release] Fix compilation with OpenSSL 1.1.1

[BKPepe]

I'm cross-compiling release/4.2 for OpenWrt (and in their master, they're using OpenSSL 1.1.1b) and even tvheadend version 4.2.8 was tagged on 12th January 2019, there wasn't included PR #1217 , which was merged on 21st November 2018. Would be nice to have it included in the next stable version.

When I have included all the commits from @neheb, I have been able to successfully compile it. I will test it later on my router.

Otherwise release/4.2 (together with tagged version 4.2.8) ends up with output:

cc1: note: someone does not honour COPTS correctly, passed 2 times
src/main.c: In function 'main':
src/main.c:1356:3: error: implicit declaration of function 'ENGINE_cleanup'; did you mean 'EVP_PBE_cleanup'? [-Werror=implicit-function-declaration]
   ENGINE_cleanup();
   ^~~~~~~~~~~~~~
   EVP_PBE_cleanup
cc1: all warnings being treated as errors
make[3]: *** [Makefile:643: /home/pepe/work/turrisos40/omnia-hbd/build/build_dir/target-arm_cortex-a9+vfpv3_musl_eabi/tvheadend-release-4.2/build.linux/src/main.o] Error 1
make[3]: Leaving directory '/home/pepe/work/turrisos40/omnia-hbd/build/build_dir/target-arm_cortex-a9+vfpv3_musl_eabi/tvheadend-release-4.2'
make[2]: *** [Makefile:105: /home/pepe/work/turrisos40/omnia-hbd/build/build_dir/target-arm_cortex-a9+vfpv3_musl_eabi/tvheadend-release-4.2/.built] Error 2