[e-acsl/doc] adapt mans to new theme

doc/frama-c-book.cls

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

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

src/plugins/e-acsl/doc/userman/examples/instrumented_first.c

src/plugins/e-acsl/doc/userman/limitations.tex

src/plugins/e-acsl/doc/userman/provides.tex