Reed-Solomon (zfec): fixed fec_new fail

With current zfec code, fec_init() needs to be called prior to fec_new(),
otherwise the later one returns NULL.

\+ updated submodule to the current zfec version (requiring fec_init();
but UG will compile with the older zfec version as well)

configure.ac

@@ -2554,6 +2554,19 @@ if test $cross_compile = no && test "$zfec_req" != no; then
                 fi
                 AC_CHECK_FILES([$ZFEC_PREFIX/fec.c $ZFEC_PREFIX/fec.h], [found_zfec=yes])
         fi
+        if test "$found_zfec" = yes; then
+                AC_MSG_CHECKING([fec_init declaration in $ZFEC_PREFIX/fec.h])
+                AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+                                   #include "$ZFEC_PREFIX/fec.h"
+                                   ]],
+                                   [[
+                                    #pragma GCC diagnostic error "-Wimplicit-function-declaration"
+                                    fec_init();]])], fec_init=yes, fec_init=no)
+                if test "$fec_init" = yes; then
+                        AC_DEFINE([HAVE_FEC_INIT], [1], [fec_init must be called before fec_new])
+                fi
+                AC_MSG_RESULT($fec_init)
+        fi
 fi
 
 if test "$found_zfec" = yes; then

src/host.cpp

@@ -99,6 +99,13 @@
 #define X11_LIB_NAME "libX11.so.6"
 #endif
 
+#ifdef HAVE_FEC_INIT
+#define restrict __restrict // not a C++ keyword
+extern "C" {
+#include <fec.h>
+}
+#endif
+
 #ifdef __linux__
 #include <mcheck.h>
 #endif
@@ -431,6 +438,10 @@ struct init_data *common_preinit(int argc, char *argv[])
                 incompatible_features = true;
         }
 
+#ifdef HAVE_FEC_INIT
+        fec_init();
+#endif
+
         return new init_data{init};
 }