ruleutils with pretty-print option

The attached patches will add
pg_get_ruledef(oid, int)
pg_get_viewdef(text, int)
pg_get_viewdef(oid, int)
pg_get_indexdef(oid, int)
pg_get_constraintdef(oid, int)
pg_get_expr(text, oid, int)

If the last parameter "pretty-print" is 0, these function will return
the same result as their original counterparts without that parameter.
The source is based on ruleutils.c 1.143, and should return exactly the
same result as before if no pretty-print is selected. My tests didn't
show any differences for pg_dump output with old or new version.

The pretty-print parameter is evaluated bit-wise.

PRETTY_PAREN 1 - Parentheses are checked; only necessary parentheses will be emitted.

PRETTY_INDENT 2 - pretty indentation and line formatting is performed

PRETTY_OPPAREN 4 - For T_BoolExpr operators, AND/OR/NOT precedence is checked, for T_OpExpr +-*/%
precedence is checked. If precedence is identified, parentheses are omitted.
This option is only active if PRETTY_PAREN is also used.

Regards,
Andreas