linux-user: Add an api to print enumareted argument values with strace

linux-user: Add an api to print enumareted argument values with strace

This patch introduces a type 'struct enums' and function 'print_enums()'
that can be used to print enumerated argument values of some syscalls
in strace. This can be used in future strace implementations.

Also, macros 'ENUM_GENERIC()', 'ENUM_TARGET()' and 'ENUM_END', are
introduced to enable automatic generation of aproppriate enumarated
values and their repsective string representations (these macros are
exactly the same as 'FLAG_GENERIC()', 'FLAG_TARGET()' and 'FLAG_END').

Future patches are planned to modify all existing print functions in
'strace.c' that print arguments of syscalls with enumerated values to
use this new api.

Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200811164553.27713-5-Filip.Bozuta@syrmia.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>