[Libc] add spec and stub for fmemopen

share/libc/stdio.c

share/libc/stdio.h

src/plugins/value/utils/library_functions.ml

...plugins/variadic/tests/erroneous/oracle/printf.res.oracle

src/plugins/variadic/tests/known/oracle/printf.res.oracle

...variadic/tests/known/oracle/printf_garbled_mix.res.oracle

...variadic/tests/known/oracle/printf_wrong_arity.res.oracle

...iadic/tests/known/oracle/printf_wrong_pointers.res.oracle

...variadic/tests/known/oracle/printf_wrong_types.res.oracle

src/plugins/variadic/tests/known/oracle/scanf.res.oracle

...plugins/variadic/tests/known/oracle/scanf_loop.res.oracle

...lugins/variadic/tests/known/oracle/scanf_wrong.res.oracle

src/plugins/variadic/tests/known/oracle/snprintf.res.oracle

...lugins/variadic/tests/known/oracle/stdio_print.res.oracle

...plugins/variadic/tests/known/oracle/stdio_scan.res.oracle

src/plugins/variadic/tests/known/oracle/swprintf.res.oracle

src/plugins/variadic/tests/known/oracle/wchar.res.oracle

tests/idct/oracle/ieee_1180_1990.res.oracle

tests/libc/oracle/fc_libc.1.res.oracle

tests/libc/oracle/netdb_c.res.oracle