[FEATURE] Add devIP as keyword for IP condition

When using an IP condition, support using keyword "devIP" to compare
the current Request IP against the devIpMask setting.

Usage:
[IP = devIP]
page.20 = TEXT
page.20.value = Hello Developer!
[end]

Fixes: #50092
Documentation: #52827
Releases: 6.2
Change-Id: I6b9128a9ac23b8d24ec1874dbe477503b20b58b8
Reviewed-on: https://review.typo3.org/24754
Reviewed-by: Ernesto Baschny
Reviewed-by: Gaëtan MARMASSE
Tested-by: Gaëtan MARMASSE
Reviewed-by: Paul Rohrbeck
Tested-by: Paul Rohrbeck
Reviewed-by: Dmitry Dulepov
Tested-by: Dmitry Dulepov
Reviewed-by: Oliver Hader