libebook: Reduce code-duplication in e_book_query_from_string()
libebook: Reduce code-duplication in e_book_query_from_string()

Merge almost identical sexp handlers used by that functions.
Also merge two de-facto identical error branches.

tintou/evolution-data-server,tintou/evolution-data-server,Distrotech/evolution-data-server,matzipan/evolution-data-server,Distrotech/evolution-data-server,tintou/evolution-data-server,Distrotech/evolution-data-server,Distrotech/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,Distrotech/evolution-data-server