avoid specifying --delim unless required

This increases portability of generated module files to versions of
environment_modules hearkening back to just after the turn of the
millennium.

lib/spack/spack/modules.py

@@ -530,13 +530,6 @@ def prerequisite(self, spec):
 class TclModule(EnvModule):
     name = 'tcl'
     path = join_path(spack.share_path, "modules")
-    environment_modifications_formats = {
-        PrependPath: 'prepend-path --delim "{separator}" {name} \"{value}\"\n',
-        AppendPath: 'append-path   --delim "{separator}" {name} \"{value}\"\n',
-        RemovePath: 'remove-path   --delim "{separator}" {name} \"{value}\"\n',
-        SetEnv: 'setenv {name} \"{value}\"\n',
-        UnsetEnv: 'unsetenv {name}\n'
-    }
 
     autoload_format = ('if ![ is-loaded {module_file} ] {{\n'
                        '    puts stderr "Autoloading {module_file}"\n'
@@ -575,6 +568,41 @@ def header(self):
             header += '}\n\n'
         return header
 
+    def process_environment_command(self, env):
+       environment_modifications_formats_colon = {
+           PrependPath: 'prepend-path {name} \"{value}\"\n',
+           AppendPath: 'append-path   {name} \"{value}\"\n',
+           RemovePath: 'remove-path   {name} \"{value}\"\n',
+           SetEnv: 'setenv {name} \"{value}\"\n',
+           UnsetEnv: 'unsetenv {name}\n'
+       }
+       environment_modifications_formats_general = {
+           PrependPath: 'prepend-path --delim "{separator}" {name} \"{value}\"\n',
+           AppendPath: 'append-path   --delim "{separator}" {name} \"{value}\"\n',
+           RemovePath: 'remove-path   --delim "{separator}" {name} \"{value}\"\n',
+           SetEnv: 'setenv {name} \"{value}\"\n',
+           UnsetEnv: 'unsetenv {name}\n'
+       }
+       for command in env:
+           # Token expansion from configuration file
+           name = command.args.get('name', '').format(**self.upper_tokens)
+           value = str(command.args.get('value', '')).format(**self.tokens)
+           command.update_args(name=name, value=value)
+           # Format the line int the module file
+           try:
+               if command.args.get('separator', ':') == ':':
+                   yield environment_modifications_formats_colon[type(
+                       command)].format(**command.args)
+               else:
+                   yield environment_modifications_formats_general[type(
+                       command)].format(**command.args)
+           except KeyError:
+               message = ('Cannot handle command of type {command}: '
+                          'skipping request')
+               details = '{context} at {filename}:{lineno}'
+               tty.warn(message.format(command=type(command)))
+               tty.warn(details.format(**command.args))       
+
     def module_specific_content(self, configuration):
         naming_tokens = self.tokens
         # Conflict