fixed leaks in test cases (#1247)

samples/sample_x86.c

@@ -301,6 +301,7 @@ static void test_i386_map_ptr(void)
         printf(">>> Failed to read 4 bytes from [0x%x]\n", ADDRESS);
 
     uc_close(uc);
+    free(mem);
 }
 
 static void test_i386_jump(void)

samples/sample_x86_32_gdt_and_seg_regs.c

@@ -280,6 +280,7 @@ static void gdt_demo()
     assert(memcmp(buf, "\x67\x45\x23\x01\xef\xcd\xab\x89", 8) == 0);
 
     uc_close(uc);
+    free(gdt);
 }
 
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