Add async support for calling functions in misc-functions.sh:

Add async support for calling functions in misc-functions.sh:

* Create a new MiscFunctionsProcess class derived from SpawnProcess.

* Add "background" support to the SpawnProcess class and split out a
  _spawn() template function so MiscFunctionsProcess can override it.

* Rename the existing EbuildPhase class to EbuildProcess.

* Create a new EbuildPhase class derived from CompositeTask. This class
  spawns the EbuildProcess and MiscFunctionsProcess classes as sub-tasks.

svn path=/main/trunk/; revision=11072