As Mark's suggestion, rename libpng_1.2.50 to libpng12 that
multi-versions libpng could coexist.
We want to make sure we have both the old and new versions to meet LSB
compliance (for people who have that enabled) as well as the new version
for newer applications.
And drop link files that conflict with higher version.
[YOCTO #4221]
Signed-off-by: Kang Kai <kai.kang@windriver.com> CC: Mark Hatle <mark.hatle@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
