be a bit more verbouse if fread fails

git-svn-id: http://svn.berlios.de/svnroot/repos/sems/trunk@966 8eb893ce-cfd4-0310-b710-fb5ebe64c474

core/plug-in/wav/wav_hdr.c

@@ -58,7 +58,11 @@
 
 #define SAFE_READ(buf,s,fp,sr) \
     sr = fread(buf,s,1,fp);\
-    if((sr != 1) || ferror(fp)) return -1;
+    if((sr != 1) || ferror(fp)) { \
+      ERROR("fread: %s (sr=%d)\n", strerror(errno), sr);	\
+    return -1;					\
+    }
+\
 
 /** \brief The file header of RIFF-WAVE files (*.wav). 
  * Files are always in