indent(1): add new -sac and -U options.

Add -sac (space after cast) and -nsac options.
These control whether space character is put after a cast operator or not.
Default is -nsac.

Add -U option for providing a file containing list of types.
This is needed for properly deciding which asterisks denote unary
operation and which denote binary.

These come from PostgreSQL.

Reference:
https://github.com/pstef/freebsd_indent/commit/84b00e3d46dfd6d955b2f481a1f3b275de9ad6d1
https://github.com/pstef/freebsd_indent/commit/49c52cf383fa2a246a1a22c6640a5a21b0f1fd90

Differential Revision: https://reviews.freebsd.org/D6966 (Partial)
Submitted by: Piotr Stefaniak