simplify includes in from/to str parsers/composers

aconvert2/src/DotConverter.cpp

aconvert2/src/GasTexConverter.cpp

aconvert2/src/TikZConverter.cpp

aconvert2/src/aconvert.cpp

...o/test-src/grammar/generate/GrammarGenerateUpToLength.cpp

alib2algo/test-src/regexp/RegExpTest.cpp

alib2algo/test-src/regexp/transform/RegExpDerivationTest.cpp

alib2algo/test-src/regexp/transform/RegExpIntegralTest.cpp

alib2str/src/StringApi.cpp

alib2str/src/StringApi.hpp

alib2str/src/alphabet/SymbolFromStringLexer.cpp

alib2str/src/alphabet/SymbolFromStringLexer.h

alib2str/src/alphabet/SymbolFromStringParser.cpp

alib2str/src/alphabet/SymbolFromStringParser.h

alib2str/src/alphabet/SymbolStringApi.cpp

alib2str/src/alphabet/SymbolStringApi.hpp

alib2str/src/alphabet/SymbolToStringComposer.cpp

alib2str/src/automaton/AutomatonFromStringLexer.cpp

alib2str/src/automaton/AutomatonFromStringLexer.h

alib2str/src/automaton/AutomatonFromStringParser.cpp