moved the entries up one folder, added the folder to the keywords

games/libpng.md

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+# libpng
+
+_libpng is the official PNG reference library._
+
+- Home: http://libpng.org/pub/png/libpng.html, https://libpng.sourceforge.io/
+- Media: https://en.wikipedia.org/wiki/Libpng
+- State: mature
+- Download: (see home)
+- Keywords: library
+- Code repository: https://github.com/glennrp/libpng.git, https://sourceforge.net/p/libpng/code/ci/master/tree/
+- Code language: C
+- Code license: Custom (see LICENSE)
+
+[libpng](https://sourceforge.net/p/libpng/code/ci/master/tree/LICENSE)
+
+## Building
+
+2017-12
+- On Windows CMake fails with "No CMAKE_ASM_COMPILER could be found." on "project(.. ASM)" with MSVC 2015 as generator
+