see #12186 - add more projections
The list of projections is now generated during the build process: scripts/BuildEpsgList.java runs and creates data/projection/custom-epsg which is generated by combining data_nodist/projection/josm-epsg (a list maintained by the JOSM team) and data_nodist/projection/epsg (an upstream list from the proj.4 project, git: 3795cdf)
The ant task epsg cares for this.