Added parameterized URI support.
* src/main.cc: -Z option added.
* src/OptionHandlerFactory.cc
* src/prefs.h: Added PREF_FORCE_SEQUENTIAL.
* src/PStringDatum.h: New class.
* src/PStringSegment.{h,cc}: New class.
* src/PStringNumLoop.h: New class.
* src/PStringSelect.h: New class.
* src/NumberDecorator.h: New class.
* src/FixedWidthNumberDecorator.h: New class.
* src/AlphaNumberDecorator.h: New class.
* src/PStringVisitor.h: New class.
* src/PStringBuildVisitor.{h,cc}: New class.
* src/ParameterizedStringParser.{h,cc}: New class.
* src/Util.{h,cc}
(isNumber): New function.
(isLowercase): New function.
(isUppercase): New function.
(alphaToNum): New function.
* test/ParameterizedStringParserTest.cc: New class.
* test/AlphaNumberDecoratorTest.cc: New class.
* test/PStringBuildVisitorTest.cc: New class.
* test/UtilTest.cc
(testIsNumber): New function.
(testIsLowercase): New function.
(testIsUppercase): New function.
(testAlphaToNum): New function.
Added '\n' after the error message
* src/RequestInfo.h (printDownloadAbortMessage)