rename two functions according to 2a3678c7:
* rtl_getCommandArg -> rtl_getAppCommandArg
* rtl_getCommandArgCount -> rtl_getAppCommandArgCount

Change-Id: I4bd3699640b03a062868b1f92fd6d78d75f5b3d4
Reviewed-on: https://gerrit.libreoffice.org/59910
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>