RFR: Allow using a system installed libpng

[Magnus Ihse Bursie]

On 2014-02-03 18:43, Omair Majid wrote:
> Hi,
>
> The following webrevs modify the build system to allow building against
> the system-installed copy of libpng as well as using the bundled copy of
> libpng
>
> ROOT: http://cr.openjdk.java.net/~omajid/webrevs/system-libpng/01/
> JDK: http://cr.openjdk.java.net/~omajid/webrevs/system-libpng/01-jdk/
>
> A new configure option `--with-libpng` is introduced which defaults to
> `bundled` but can be set to `system` to use the system-installed copy of
> libpng.

Thank you for the patch!

Looks good to me (but I'm no formal reviewer), apart from this line in 
libraries.m4:
       with_libpng=${DEFAULT_libpng}

which should be DEFAULT_LIBPNG, I assume, otherwise the default case 
will not work.

Due to this, I'd like to ask you to please double check that 
--with-libpng=system | bundled | invalid-value | <empty>, and no flag at 
all, all work as expected.

/Magnus