build: hedge lavc depends

Allow linking libavcodec conversions outside UG with reasonably small
amount of dependencies.

src/libavcodec/lavc_common.c

@@ -190,15 +190,20 @@ static void av_log_ug_callback(void *avcl, int av_level, const char *fmt, va_lis
         buf[0] = '\0';
 }
 
+#ifdef HAVE_CONFIG_H // built inside UG
 ADD_TO_PARAM("lavcd-log-level",
                 "* lavcd-log-level=<num>[U][D]\n"
                 "  Set libavcodec log level (FFmpeg range semantics, unless 'U' suffix, then UltraGrid)\n"
                 " - 'D' - use FFmpeg default log handler\n");
+#endif
 /// Sets specified log level either given explicitly or from UG-wide log_level
 void ug_set_av_logging() {
         av_log_set_level(uv_to_av_log(log_level));
         av_log_set_callback(av_log_ug_callback);
-        const char *param = get_commandline_param("lavcd-log-level");
+        const char *param = NULL;
+#ifdef HAVE_CONFIG_H // built inside UG
+        param = get_commandline_param("lavcd-log-level");
+#endif
         if (param == NULL) {
                 return;
         }

src/utils/thread.c

@@ -37,14 +37,14 @@
 
 #ifdef HAVE_CONFIG_H
 #include "config.h"
-#include "config_unix.h"
-#include "config_win32.h"
 #endif
 
 #include <libgen.h>
 #ifdef HAVE_SETTHREADDESCRIPTION
 #include <processthreadsapi.h>
 #endif
+#include <stdlib.h>
+#include <string.h>
 
 #include "debug.h"
 #include "host.h"

src/utils/worker.cpp

@@ -35,17 +35,13 @@
  * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifdef HAVE_CONFIG_H
-#include "config.h"
-#include "config_unix.h"
-#include "config_win32.h"
-#endif // HAVE_CONFIG_H
-
 #include "utils/misc.h" // get_cpu_core_count
 #include "utils/thread.h"
 #include "utils/worker.h"
 
+#include <cassert>
 #include <algorithm>
+#include <pthread.h>
 #include <queue>
 #include <set>
 #include <vector>