Improved error reporting if external process could not be executed.
Fixed one Java 1.4 incompatibility in RegionsTreePanel.java.
Removed some debug statements.
M src/edu/rice/cs/drjava/config/DrJavaPropertySetup.java
M src/edu/rice/cs/drjava/ui/ExternalProcessPanel.java
M src/edu/rice/cs/drjava/ui/RegionsTreePanel.java
M src/edu/rice/cs/drjava/ui/ExecuteExternalDialog.java
M src/edu/rice/cs/util/FileOps.java
M src/edu/rice/cs/util/ProcessChain.java
A src/edu/rice/cs/util/JoinInputStream.java
M src/edu/rice/cs/util/GeneralProcessCreator.java
M src/edu/rice/cs/util/ProcessSequence.java
M src/edu/rice/cs/util/ProcessCreator.java