cmd: add asn1_compiler

Imported from linux kernel v5.3:
 asn1.h without changes
 asn1_ber_bytecode.h without changes
 asn1_decoder.h without changes
 asn1_compiler.c without changes

This host command will be used to create a ASN1 parser, for example,
for pkcs7 messages or x509 certificates. More specifically, it will
generate *byte code* which will be interpreted by asn1 decoder library.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>