pgcrypto warnings for Sun's cc

This patch removes a couple of warnings Sun's cc reports in
contrib/pgcrypto.

cc -Xa -v -g -KPIC -I. -I../../src/include -I/usr/local/include -c -o sha2.o sha2.c
"sha2.c", line 173: warning: storage class after type is obsolescent
"sha2.c", line 193: warning: storage class after type is obsolescent
"sha2.c", line 205: warning: storage class after type is obsolescent
"sha2.c", line 249: warning: storage class after type is obsolescent
"sha2.c", line 261: warning: storage class after type is obsolescent

Kris Jurka