Fix a lot of compile errors on unix.

src/interfaces/odbc/GNUmakefile

src/interfaces/odbc/convert.c

src/interfaces/odbc/info.c

src/interfaces/odbc/isql.h

src/interfaces/odbc/odbcapi.c

src/interfaces/odbc/odbcapi30.c

src/interfaces/odbc/pgapifunc.h

src/interfaces/odbc/pgtypes.c

src/interfaces/odbc/statement.c