/usr/include/ is in libecpg-dev 9.3.4-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/postgresql/
/usr/include/postgresql/pgtypes_interval.h
/usr/include/postgresql/ecpg_config.h
/usr/include/postgresql/ecpglib.h
/usr/include/postgresql/sqlca.h
/usr/include/postgresql/sqlda.h
/usr/include/postgresql/pgtypes_error.h
/usr/include/postgresql/ecpgtype.h
/usr/include/postgresql/pgtypes_numeric.h
/usr/include/postgresql/sqlda-compat.h
/usr/include/postgresql/sqlda-native.h
/usr/include/postgresql/pgtypes_date.h
/usr/include/postgresql/informix/
/usr/include/postgresql/informix/esql/
/usr/include/postgresql/informix/esql/datetime.h
/usr/include/postgresql/informix/esql/sqltypes.h
/usr/include/postgresql/informix/esql/decimal.h
/usr/include/postgresql/ecpg_informix.h
/usr/include/postgresql/sql3types.h
/usr/include/postgresql/pgtypes_timestamp.h
/usr/include/postgresql/ecpgerrno.h