worldclock: fix linking issue with malloc

worldclock: fix linking issue with malloc

The Worldclock was using 'malloc' to construct Edje_Message_Int_Set struct.
This leads to problems on Tizen SDK 4.0 build, when during linking
'malloc' symbol was resolved not from glibc, but from libchromium-ewk.so.

This lead to crash when trying to use chromium's malloc.

Due to way how SDK build system works, I cannot remove libchromium from link options.
Instead I removed all usage of malloc in code.

Additionally add static to internal function

Change-Id: I87d188b959dfdedd175986ac102b46db062964a9