Bug in GladeWin32 package.
I installed the latest GladeWin32 package (2.8.18)
When using pkg-config (through MinGW and MSYS) I
discovered that the .pc file for libpng12 was named
libpng13 by accident. It was the cairo file that didn't
find the correct one. I viewed the libpng13.pc file and
found all occurences of 'libpng' appended with '12',
not '13', so I changed the name of the file, and
voila!, the compile worked (I had to set the
PKG_CONFIG_PATH myself though, another thing that
should be fixed automatically
in the next release).