Fix issue with variable arguments.
Fix issue with variable arguments.

Variable arguments field_offsets were being used outside the va_start/va_end block.

pombredanne/yara,hillu/yara,cblichmann/yara,pombredanne/yara,VirusTotal/yara,wxsBSD/yara,cblichmann/yara,cblichmann/yara,VirusTotal/yara,hillu/yara,VirusTotal/yara,wxsBSD/yara,wxsBSD/yara,pombredanne/yara,cblichmann/yara,hillu/yara,hillu/yara,pombredanne/yara,cblichmann/yara,hillu/yara,pombredanne/yara,VirusTotal/yara,VirusTotal/yara,wxsBSD/yara,wxsBSD/yara