update ebuild to EAPI 5, and adjust system

Signed-off-by: Lan Yixun (dlan) <dennis.yxun@gmail.com>
add USE=doc support, but make it disabled default

Signed-off-by: Lan Yixun (dlan) <dennis.yxun@gmail.com>
backport upstream patches, fix build system issue

Signed-off-by: Lan Yixun (dlan) <dennis.yxun@gmail.com>
make USE=test optional, also disabled by default

Signed-off-by: Lan Yixun (dlan) <dennis.yxun@gmail.com>
add qmimodem driver

Signed-off-by: Lan Yixun (dlan) <dennis.yxun@gmail.com>
add USE dundee

Signed-off-by: Lan Yixun (dlan) <dennis.yxun@gmail.com>
add GPRS provision USE support

Signed-off-by: Lan Yixun (dlan) <dennis.yxun@gmail.com>
add datafiles USE flag support

Signed-off-by: Lan Yixun (dlan) <dennis.yxun@gmail.com>
explicitly disable maintainer-mode

Signed-off-by: Lan Yixun (dlan) <dennis.yxun@gmail.com>