pgsql: Properly identify mingw as a win32 platform needing different

Log Message:
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Properly identify mingw as a win32 platform needing different diff
options to deal with strange line endings.

Modified Files:
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pgsql/src/interfaces/ecpg/test:
pg_regress_ecpg.c (r1.1 -> r1.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/pg_regress_ecpg.c.diff?r1=1.1&r2=1.2)