Add documentation for rva field in resources.
Add documentation for rva field in resources.

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