doc: Modernize steps to be followed after release

Remove old references to sourceforge, add what actually should be done
and provide some more details.
build: Fix windows configure when using --with-qt-libdir

fixes #4630

Github-Pull: #4633
Merge pull request #4626

e1eb741 doc: Modernize steps to be followed after release (Wladimir J. van der Laan)
Add travis CI builds.
Add openssl specific config. test.
Move pkg.m4 with other m4 scripts.
Add minimal bitcoin.pc.in.
Replacd deprecated INCLUDES with DEPS_INCLUDES.
Fix. Add in bitcoin.pc.in.