Remove length limit on PKINIT PKCS#12 prompt

Long pathnames can trigger the 128-byte prompt length limit in
pkinit_get_certs_pkcs12.  Use asprintf instead of snprintf.  Also
check the result of the prompter invocation.

ticket: 8011
target_version: 1.13.1
tags: pullup
Adjust asn1c test vector code for new asn1c

asn1c 0.9.22 added support for representing integers using unsigned
types if they have appropriate constraints.  This changes the
representation of RFC4120's UInt32 type from Integer_t to unsigned
long.  In make-vectors.c, this means we can use a static initializer
for kvno, and that the old method of calling asn_long2INTEGER doesn't
work.  Adjust make-vectors.c to assume the newer version of asn1c.