From Jean-Sebastien Guay, build fixes for Mingw

src/osgPlugins/jpeg/ReaderWriterJPEG.cpp

@@ -70,6 +70,14 @@ namespace osgDBJPEG
 
 static int jpegerror = ERR_NO_ERROR;
 
+/* Some versions of jmorecfg.h define boolean, some don't...
+   Those that do also define HAVE_BOOLEAN, so we can guard using that. */
+#ifndef HAVE_BOOLEAN
+  typedef int boolean;
+  #define FALSE 0
+  #define TRUE 1
+#endif
+
 /* CODE FOR READING/WRITING JPEG FROM STREAMS
  *  This code was taken directly from jdatasrc.c and jdatadst.c (libjpeg source)
  *  and modified to use a std::istream/ostream* instead of a FILE*