If we're not making asn1buf_insert_octet an inline function, then make

If we're not making asn1buf_insert_octet an inline function, then make
asn1buf_size, asn1buf_ensure_space, and asn1buf_expand static in
asn1buf.c, for better optimization.

Recode asn1buf_ensure_space to directly return the result of asn1buf_expand.
Don't check for NULL before malloc/realloc in asn1buf_expand.

Fix a couple minor signedness warnings.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@20957 dc483132-0cff-0310-8789-dd5450dbe970