[Kernel] add support for _Static_assert

share/libc/assert.h

src/kernel_internals/parsing/clexer.mll

src/kernel_internals/parsing/cparser.mly

src/kernel_internals/typing/cabs2cil.ml

src/kernel_services/ast_printing/cabs_debug.ml

src/kernel_services/ast_printing/cil_printer.ml

src/kernel_services/ast_printing/cprint.ml

src/kernel_services/parsetree/cabs.mli

src/kernel_services/parsetree/cabshelper.ml

src/kernel_services/visitors/cabsvisit.ml

src/plugins/metrics/metrics_cabs.ml

tests/syntax/oracle/static_assert.0.res.oracle

tests/syntax/oracle/static_assert.1.res.oracle

tests/syntax/static_assert.c