RFR: JDK-8148629: Disable remaining warnings in awt/fontmanager

[Erik Joelsson]

A while back, Magnus did a tremendous job of disabling most warnings in 
the JDK native libraries and enabling warnings as errors on most of 
them. However, some libraries, typically awt related, proved to be harder.

One of the reasons was that some toolchains had different warning labels 
specified for C vs C++ and would not accept the other kind without 
printing new warning. For libraries containing both C and C++ source 
files, this prevented us from disabling all warnings. This limitation in 
SetupNativeCompilation has since been fixed so I could use that 
functionality to disable most remaining warnings.

Another reason is that some source files contain warnings that are 
deemed severe enough by the compiler that they can't be individually 
ignored. Since the team owning that source seem unwilling to fix these 
warnings anyway, I have simply disabled all warnings on those specific 
files, for the specific toolchains where it applies. I have tried to add 
descriptive comments explaining each such occurrence.

I have tested this by building a full hotspot job and an openjdk only 
job in JPRT. It is possible that people building with other toolchain 
versions than Oracle will start seeing new build failures because of 
more warnings in these libraries. In that case, either 
--disable-warnings-as-errors, submit fixes for the warnings, or add more 
warning ignores.

Bug: https://bugs.openjdk.java.net/browse/JDK-8148629
Webrev: http://cr.openjdk.java.net/~erikj/8148629/webrev.jdk.01/

/Erik