Change conditional USE deps syntax and expermental EAPI from 2_pre0 to 2_pre1.

Change conditional USE deps syntax and expermental EAPI from 2_pre0 to 2_pre1.

Conditional syntax examples:

	Compact Form        Equivalent Expanded Form

	foo[bar?]           bar? ( foo[bar]  ) !bar? ( foo       )
	foo[!bar?]          bar? ( foo       ) !bar? ( foo[-bar] )
	foo[bar=]           bar? ( foo[bar]  ) !bar? ( foo[-bar] )
	foo[!bar=]          bar? ( foo[-bar] ) !bar? ( foo[bar]  )

svn path=/main/trunk/; revision=11274