Fix compiler warning in IRutils_test.cpp (#756)
Fix compiler warning in IRutils_test.cpp (#756)

Make the test array >= 8 entries.
To remove the following warning:
```
g++ -isystem ../lib/googletest/googletest/include -DUNIT_TEST -g -Wall -Wextra -pthread -std=gnu++11 -I../src -I. -c IRutils_test.cpp
In file included from IRutils_test.cpp:6:0:
IRutils_test.cpp: In member function ‘virtual void TestResultToRawArray_LargeValues_Test::TestBody()’:
IRrecv_test.h:12:25: warning: comparison is always false due to limited range of data type [-Wtype-limits]
   for (uint8_t i = 0; i < c / 8; ++i) {         \
                         ^
IRutils_test.cpp:477:3: note: in expansion of macro ‘EXPECT_STATE_EQ’
   EXPECT_STATE_EQ(test_data, result, 7);
   ^
```
markszabo/IRremoteESP8266,markszabo/IRremoteESP8266,markszabo/IRremoteESP8266,markszabo/IRremoteESP8266