TurboJPEG: Add lossless JPEG detection capability

Add a new TurboJPEG C API function (tjDecompressHeader4()) and Java API
method (TJDecompressor.getFlags()) that return the bitwise OR of any
flags that are relevant to the JPEG image being decompressed (currently
TJFLAG_PROGRESSIVE, TJFLAG_ARITHMETIC, TJFLAG_LOSSLESS, and their Java
equivalents.)  This allows a calling program to determine whether the
image being decompressed is a lossless JPEG image, which means that the
decompression scaling feature will not be available and that a
full-sized destination buffer should be allocated.

More specifically, this fixes a buffer overrun in TJBench, TJExample,
and the decompress* fuzz targets that occurred when attempting (in vain)
to decompress a lossless JPEG image with decompression scaling enabled.

turbojpeg-mapfile.jni

@@ -99,3 +99,9 @@ TURBOJPEG_2.0
     tjLoadImage;
     tjSaveImage;
 } TURBOJPEG_1.4;
+
+TURBOJPEG_2.2
+{
+  global:
+    tjDecompressHeader4;
+} TURBOJPEG_2.0;