Merge pull request #11417 from Turim:imgcodecs_cmake_decoders_customize_formats

* imgcodecs cmake: the option to customize supported formats list (WITH_IMGCODEC_HDR, WITH_IMGCODEC_SUNRASTER, WITH_IMGCODEC_PXM)

* imgcodecs: fixes

- fixed CMake scripts (=OFF doesn't really work)
- restore dropped GDCM block
- added _IMGCODEC_ prefix
- fixed tests
- include PAM format under WITH_IMGCODEC_PXM option

modules/imgcodecs/src/grfmt_hdr.cpp

@@ -44,6 +44,8 @@
 #include "grfmt_hdr.hpp"
 #include "rgbe.hpp"
 
+#ifdef HAVE_IMGCODEC_HDR
+
 namespace cv
 {
 
@@ -166,3 +168,5 @@ bool HdrEncoder::isFormatSupported( int depth ) const {
 }
 
 }
+
+#endif // HAVE_IMGCODEC_HDR