Strings shorter than 128 bytes collide possible due to the implementation details of MurmurHash3_x64_128(). Especially, the hash value seems to depend on the length of such a string.
For such a short string, we concatenate it as many times as needed to make it longer than 128 bytes.
Added a test to show hash results.

For example, before this fix, test_murmur3 3 1024 data1.txt data2.txt data3.txt 123456.txt 1data5.txt data91.txt showed the following results

data1.txt	199.ca.3e.data1.txt
data2.txt	199.ca.3e.data2.txt
data3.txt	199.ca.3e.data3.txt
123456.txt	37e.c8.89.123456.txt
1data5.txt	37e.c8.89.1data5.txt
data91.txt	37e.c8.89.data91.txt

After the fix, the below is the new results.

data1.txt	2cd.1cd.3cc.data1.txt
data2.txt	11f.2cb.5a.data2.txt
data3.txt	22b.28f.11d.data3.txt
123456.txt	db.272.14.123456.txt
1data5.txt	8a.1ce.f8.1data5.txt
data91.txt	219.32f.47.data91.txt