[eacsl:doc] Update reference manual according to ACSL 1.16

src/plugins/e-acsl/doc/refman/assertions.tex

src/plugins/e-acsl/doc/refman/biblio.bib

src/plugins/e-acsl/doc/refman/changes_modern.tex

src/plugins/e-acsl/doc/refman/fn_behavior.tex

src/plugins/e-acsl/doc/refman/generalinvariants.tex

src/plugins/e-acsl/doc/refman/ghost.tex

src/plugins/e-acsl/doc/refman/loops.tex

src/plugins/e-acsl/doc/refman/main.tex

src/plugins/e-acsl/doc/refman/speclang_modern.tex