cleanup

library/libpng.md

@@ -5,7 +5,8 @@ _libpng is the official PNG reference library._
 - Home: http://libpng.org/pub/png/libpng.html
 - Wikipedia: https://en.wikipedia.org/wiki/Libpng
 - Download: see home
-- State: mature, official
+- State: mature
+- Keywords: official
 - Code: https://sourceforge.net/p/libpng/code/ci/master/tree/
 - Language(s): C
 - License: [libpng](https://sourceforge.net/p/libpng/code/ci/master/tree/LICENSE)

library/swig.md

@@ -0,0 +1,15 @@
+# SWIG
+
+_Software development tool that connects programs written in C and C++ with a variety of high-level programming languages._
+
+- Home: http://swig.org/
+- Wikipedia: https://en.wikipedia.org/wiki/SWIG
+- Download: http://www.swig.org/download.html
+- State: mature
+- Keywords: language binding, interface generator
+- Code: https://github.com/swig/swig
+- Language(s): C++
+- License: [Special](https://raw.githubusercontent.com/swig/swig/master/LICENSE)
+
+## Building
+