Moved everything that is generated to the generated folder (#6580)

Moved everything that is generated to the generated folder
merged-on-behalf-of: Andrei Alexandrescu <andralex@users.noreply.github.com>

.gitignore

@@ -1,34 +1,18 @@
 *.[oa]
 *.deps
-src/cdxxx.c
-src/debtab.c
 src/dmd
-src/dmd_frontend
-src/ddmd
-src/dmd.conf
-src/elxxx.c
-src/fltables.c
-src/id.c
-src/id.h
-src/id.d
-src/idgen
-src/optab.c
-src/optabgen
-src/tytab.c
+src/ddmd/id.d
+src/ddmd/id.h
 test/test_results
+test/trace.def
+test/trace.log
+generated/
 *.obj
-src/idgen.exe
 src/dmd.exe
-src/dmd_frontend.exe
-src/optabgen.exe
-src/verstr.h
 *.map
-.DS_Store
-trace.def
-trace.log
-Makefile
-src/magicport/magicport
-src/SYSCONFDIR.imp
+-.DS_Store
+-trace.def
+-trace.log
 
 # Visual Studio files
 *.exe