sprintf and strcpy are unsafe : buffer overflow is possible

[aka-sps]

https://github.com/riscv/riscv-openocd/blob/42be17aed602405a8a36aa06671ea7566ec3f2e4/src/target/riscv/riscv-013.c#L350

Use snprintf (Note: on buffer overflow last symbol is not '\0', need force)

https://github.com/riscv/riscv-openocd/blob/42be17aed602405a8a36aa06671ea7566ec3f2e4/src/target/riscv/riscv-013.c#L352

Use strncpy (Note: on buffer overflow last symbol is not '\0', need force)

[en-sc]

@aka-sps, I would like to close this. It is not an issue anymore. The code in question was changed by #892 and currently it is guaranteed that the buffer is sufficient.

[en-sc]

@aka-sps, I'm closing this one. Feel free to reopen, if you have any concerns.