XLM support for OCL

[kenorb]

trafficstars

$ ./oclvanitygen++ -C XLM GA
Generating XLM Address
Cannot find coin XLM in base58prefix.txt

Expected results:

$ ./vanitygen++ -C XLM GA
Generating XLM Address
XLM patterns GA
XLM Address: GAV6JH4INWYGAN54TJTPPH4FLZBUANNNNLZDAR55DCCIEYLYQUAIX566