Fix to please GCC

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58615 65644016-39b1-43b1-bf79-96bc8fe82c15
Cleanup - removed unused (always NULL) field tra_sibling from transaction class in engine

git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58616 65644016-39b1-43b1-bf79-96bc8fe82c15
Added support for systemd
Removed scripts to change firebird runuser to root and back to firebird
Removed script changing SYSDBA password (nothing except gsec call left in it)
Reorganize posix/linux install files minimizing OS-specific part of .tgz install scripts
Related cleanup and bugfixing in posix install


git-svn-id: svn+ssh://svn.code.sf.net/p/firebird/code/firebird/trunk@58617 65644016-39b1-43b1-bf79-96bc8fe82c15