Add (ice-9 format) module to imports for freeimage and ftgl

freeimage.scm and ftgl.scm were throwing warnings when running make
about a unsupported format option

GEN      2d/wrappers/freeimage.go
2d/wrappers/freeimage.scm:120:6: warning: "<freeimage-bitmap ~x width: ~d height: ~d bpp: ~d>": unsupported format option ~x, use (ice-9 format) instead
wrote `2d/wrappers/freeimage.go'
  GEN      2d/wrappers/ftgl.go
2d/wrappers/ftgl.scm:62:6: warning: "<ftgl-font ~x>": unsupported format option ~x, use (ice-9 format) instead
2d/wrappers/ftgl.scm:100:6: warning: "<ftgl-simple-layout ~x>": unsupported format option ~x, use (ice-9 format) instead
wrote `2d/wrappers/ftgl.go'
  GEN      2d/wrappers/gl.go
wrote `2d/wrappers/gl.go'

adding the modules to the module definition of each file fixes it