Edit README.asn1

Add another blank line before section headers.  Avoid contractions.
Change some whiches to thats where it seems appropriate.  Fix some
missing or extra words.
Fix error message quotations in install_kdc.rst

Some error messages that kprop could print were quoted incorrectly in
install_kdc.rst.

Also fix minor typos.

ticket: 7785 (new)
target_version: 1.12
tags: pullup
Fix S4U2Self against non-FAST KDCs

When we added FAST TGS support in 1.11, we broke S4U2Self against KDCs
which don't support FAST, because the S4U2Self padata is only present
within the FAST request.  For now, duplicate that padata in the outer
request so that both FAST and non-FAST KDCs can see it.

ticket: 7791
target_version: 1.11.5
tags: pullup
Avoid malloc(0) in SPNEGO get_input_token

If we read a zero-length token in spnego_mech.c's get_input_token(),
set the value pointer to NULL instead of calling malloc(0).

ticket: 7794 (new)