pgsql: Use $INDENT rather than indent throughout the pgindent code

Use $INDENT rather than indent throughout the pgindent code

This allows the user to change the path to be used more easily.
Also, change URL in README.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/c4d124365b9b535e8c98e4568ade3e0c15b11810

Modified Files
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src/tools/pgindent/README   |    2 +-
src/tools/pgindent/pgindent |    8 +++++---
2 files changed, 6 insertions(+), 4 deletions(-)