CHANGES.txt: Add merged PRs since alpha13
CHANGES.txt: Add merged PRs since alpha13

dcourtois/premake-core,noresources/premake-core,dcourtois/premake-core,dcourtois/premake-core,mandersan/premake-core,LORgames/premake-core,premake/premake-core,premake/premake-core,sleepingwit/premake-core,LORgames/premake-core,sleepingwit/premake-core,mandersan/premake-core,dcourtois/premake-core,LORgames/premake-core,starkos/premake-core,starkos/premake-core,starkos/premake-core,noresources/premake-core,noresources/premake-core,noresources/premake-core,premake/premake-core,dcourtois/premake-core,mandersan/premake-core,dcourtois/premake-core,noresources/premake-core,premake/premake-core,premake/premake-core,sleepingwit/premake-core,mandersan/premake-core,noresources/premake-core,premake/premake-core,starkos/premake-core,noresources/premake-core,dcourtois/premake-core,premake/premake-core,starkos/premake-core,starkos/premake-core,LORgames/premake-core,mandersan/premake-core,starkos/premake-core,sleepingwit/premake-core,sleepingwit/premake-core,LORgames/premake-core