Add staging support
Fix leftover

Reported by:	QAT
Fix leftover

Reported by:	QAT
Convert to USES=gecko
- Fix build when MODPLUG option is enabled (disabled by default)

PR:		ports/188377
Submitted by:	Volodymyr Kostyrko <arcade@b1t.name>
Support stage
- Add staging support
- Convert to new LIB_DEPENDS format, USES=gmake
- Register CONFLICTS
- Define DOCS option
Add staging support