[z1993] Fix some spell targeting

* Implement Target Type 51 as TARGET_AREAEFFECT_GO_AROUND_SOURCE
* Support spells that fill AoE targets based on source location
Thanks to Reamer for discussing these changes

Signed-off-by: Schmoozerd <schmoozerd@scriptdev2.com>

(based on commit 534a25d)

Signed-off-by: Nighoo <nighoo@gmail.com>

(cleaned version of 43bec09)

(based on commit [s1581] - 33675d0)