pgsql: Make dumpcolors() have tolerable performance when using 32-bit

Log Message:
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Make dumpcolors() have tolerable performance when using 32-bit chr,
as we do (and upstream Tcl doesn't). The loop limit might be subject
to negotiation if anyone ever tries to do regex debugging in Far
Eastern languages, but for now 1000 seems plenty. CHR_MAX was right out :-(

Modified Files:
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pgsql/src/backend/regex:
regc_color.c (r1.5 -> r1.6)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/regex/regc_color.c?r1=1.5&r2=1.6)