RFR 8056039: Hotspot does not compile with clang 3.4 on Linux

[Mikael Gerdin]

Hi all,

In order to get clang's (sometimes) more helpful error messages when compiling 
I'd like to fix the few remaining places where clang fails to compile Hotspot.

The culprit in this case was "local_vsnprintf" in os_linux.cpp, an unused 
function which wasn't annotaded with the PRINTF_FORMAT macro.
Since the function was unused I decided to remove it instead, then I found it 
in the other os_*nix.cpp files as well.

Digging into the Teamware history it looks like it first appeared in the 
Solaris port because vsnprintf did not exist on some very old versions of 
Solaris, so it was dynamically looked up through dlsym. For a few years 
vsnprintf has been present in the Solaris header files, so I think it's safe 
to remove the workaround now some 17 years later.

I also need a SCANF_FORMAT for an internal file, so I added that to 
globalDefinitions.

Webrev: http://cr.openjdk.java.net/~mgerdin/8056039/webrev/
Buglink: https://bugs.openjdk.java.net/browse/JDK-8056039

Thanks
/Mikael