[Gm2] Observation on date invocation in gm2

[john o goyo]

The call to "date" in gm2/tools-src/makeversion at line 145 passes a  
GNU-extension option.  All the other invocations are XPG4-compliant.   
Consquently, version.texi has no date because I used the XPG4 tools  
building on Solaris 10.

This does not stop the build and has been there a while.  I only  
noticed because I happened to looking at that terminal window and  
noticed the error.

john