Fix some typose in the i2d/d2i functions that

call the i2c/c2i (they were not using the
content length for the headers).

Fix ASN1 long form tag encoding. This never
worked but it was never tested since it is
only used for tags > 30.

New options to smime program to allow the
PKCS#7 format to be specified and the content
supplied externally.