Need reviewer: GNU make 3.81

[Kelly O'Hair]

Need reviewer.

This just causes a sanity warning message at build time when anything  
older than GNU make 3.81 is used.
We have run into multiple issues where the use of the older GNU make  
versions have caused problems
and there are some features such as $(eval) that only work with 3.81  
that we may want to use someday.
If and when we start using these 3.81 features, we will need to change  
this sanity warning to a fatal.

This should not impact any Linux systems, nor anyone using gmake on  
Solaris, which is usually 3.81 or newer.
On Windows, life is a little more complicated, but nothing new there.
Getting a CYGWIN GNU make 3.81 that understands the drive letter paths  
(C:/) can be a little problematic,
One from http://www.cmake.org/files/cygwin/make.exe should work.

6909026: Change GNU make version requirement to 3.81
http://cr.openjdk.java.net/~ohair/openjdk7/jdk7-build-381/webrev/

-kto