full merge of salsa/mpfr and master

Makefile.in

configure.ac

include/arrow.h

lustrec.odocl

src/Makefile.in

src/backends/C/c_backend.ml

src/backends/C/c_backend_common.ml

src/backends/C/c_backend_header.ml

src/backends/C/c_backend_main.ml

src/backends/C/c_backend_makefile.ml

src/backends/C/c_backend_src.ml

src/backends/Horn/horn_backend.ml

src/basic_library.ml

src/causality.ml

src/clock_calculus.ml

src/clocks.ml

src/compiler_common.ml

src/corelang.ml

src/corelang.mli

src/env.ml