Merge #7603: Build System: Use PACKAGE_TARNAME in NSIS script

0528e30 Remove wxwidgets references from NSIS script. (JeremyRand)
26880c3 build: Use PACKAGE_TARNAME and new bin names in NSIS script. (JeremyRand)
0dbf6e4 build: define base filenames for use elsewhere in the buildsystem (Cory Fields)