Add coverage exclusions for test code.

For some of the code e.g. doing timing measurements there is no
real point in running regression testing on it, thus it should
not be counted against coverage.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

libavutil/aes.c

@@ -259,6 +259,7 @@ int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
 }
 
 #ifdef TEST
+// LCOV_EXCL_START
 #include <string.h>
 #include "lfg.h"
 #include "log.h"
@@ -331,4 +332,5 @@ int main(int argc, char **argv)
     }
     return err;
 }
+// LCOV_EXCL_STOP
 #endif