hg: jdk7/build/jdk: 6909026: Change GNU make version requirement to 3.81

[kelly . ohair]

Changeset: 435b477c4f14
Author:    ohair
Date:      2010-12-18 18:28 -0800
URL:       http://hg.openjdk.java.net/jdk7/build/jdk/rev/435b477c4f14

6909026: Change GNU make version requirement to 3.81
Reviewed-by: robilad

! make/common/shared/Defs-versions.gmk