debian: rewrite copyright in DEP-5 format, credit all authors

The free-form debian/copyright credited only Xavier Roche, but the source
tree bundles code from other authors under additional licenses that went
unlisted: Yann Philippot (src/htsjava.*, GPL-3+), the minizip code by
Gilles Vollant, Mathias Svensson, Even Rouault and Info-ZIP (Zlib),
Colin Plumb's md5.c (public domain), and the coucal library (BSD-3-clause)
with Austin Appleby's murmurhash3.h (public domain).

Convert to machine-readable DEP-5 and add a Files stanza per component, as
requested in the Debian NEW review of 3.49.9-1.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>

src/htslib.c

@@ -5305,11 +5305,6 @@ static int get_loglevel_from_coucal(coucal_loglevel level) {
 static void default_coucal_loghandler(void *arg, coucal_loglevel level, 
                                        const char* format, va_list args) {
 
-  /* informational chatter (hashtable stats on delete, etc.) only when
-     debugging; keep warnings and critical errors always visible. */
-  if (level > coucal_log_warning && hts_dgb_init <= 0) {
-    return;
-  }
   if (level <= coucal_log_warning) {
     fprintf(stderr, "** warning: ");
   }