Add preferred shift time to the UTC time
ValidLifetime parameter: Replace localtime with UTC time
RouteLifetime parameter: Replace localtime with UTC time
IPv6 PreferredLifetime parameter: Replace localtime with UTC time
Security LastModif parameter: Replace localtime with UTC time
AssociationTime parameter: Replace localtime with UTC time
IPV6 PreferredLifetime, ValidLifetime parameter: Replace localtime with UTC time
DHCPv6 PreferredLifetime, ValidLifetime parameter: Replace localtime with UTC time
Add dm_time_utc_format function to get UTC time format
DHCPv4 LeaseTimeRemaining parameter: Replace localtime with UTC time
DeviceInfo Date parameter: Replace localtime with UTC time
DynamicDNS LastUpdate parameter: Replace localtime with UTC time
VoiceService ExpireTime parameter: Replace localtime with UTC time
Backup() parameter: Replace localtime with UTC time
- remove unused variables
- fix coding style of most function (Indentation, Tabulation, ..)
- check the source code using cppcheck tool
- change sprintf by snprintf
