- modified patch #4681, for scons compiling

of the fluidsim can now be disabled with the
	flag: BF_NO_ELBEEM='true', e.g. for irix systems.
	(The number of ifdefs from the original
	patch was reduced, and the defines are now
	only necessary when elbeem is switched off.)
- particle generation option is available again

intern/SConscript

@@ -1,4 +1,6 @@
 #!/usr/bin/python
+Import ('env')
+
 SConscript(['SoundSystem/SConscript',
             'string/SConscript',
             'ghost/SConscript',
@@ -10,7 +12,6 @@ SConscript(['SoundSystem/SConscript',
             'decimation/SConscript',
             'iksolver/SConscript',
             'boolop/SConscript',
-            'elbeem/SConscript',
             'opennl/SConscript'])
 
 # NEW_CSG was intended for intern/csg, but
@@ -19,6 +20,9 @@ SConscript(['SoundSystem/SConscript',
 # perhaps get rid of intern/csg?
 NEW_CSG='false'
 
+if env['BF_NO_ELBEEM'] == 'false':
+	SConscript(['elbeem/SConscript'])
+
 if NEW_CSG=='false':
 	SConscript(['bsp/SConscript'])
 else: