tidy: use named constant

...2algo/src/automaton/generate/NumberOfSymbolsAutomaton.cpp

...lgo/src/automaton/generate/RandomTreeAutomatonFactory.cpp

alib2algo/src/grammar/generate/RandomGrammarFactory.cpp

alib2algo/src/regexp/generate/RandomRegExpFactory.cpp

alib2algo/src/string/generate/RandomStringFactory.cpp

alib2algo/src/tree/generate/RandomTreeFactory.cpp

...go_experimental/src/automaton/RandomAutomatonFactory2.cpp

...go_experimental/src/automaton/RandomAutomatonFactory3.cpp