Fix several portability issues affecting Solaris

Fix several portability issues affecting Solaris

Commit 1bfcf572241a4ec0e44e609e5c6b7c0b11b08eea added a trailing
semicolon to the Solaris INIT_FINI_PREP, causing a syntax error when
MAKE_SHLIB_COMMAND uses it as "$(INIT_FINI_PREP} && ${LDCOMBINE} ...".
Remove it.

Commit a575589ef525fb139cafa0de1a05382845f0afbd introduced UNIX domain
socket variables named "sun", which is defined to 1 on Solaris.  Use
"unaddr" or avoid declaring a variable.

Commit 1c87ce6c44a9de0824580a2d72a8a202237e01f4 changed
pkinit_constants.c to use char arrays for OID constants, for brevity
when including them in krb5_data initializers.  But many of the array
elements are not within the range of a signed char, causing errors
with the Solaris C compiler.  Change these constants to uint8_t arrays
and introduce a macro to shorten the krb5_data initializers.

[ghudson@mit.edu: edited for style; wrote commit message]

ticket: 9195