Incremental modules build

[Mandy Chung]

  Hi Alan,

I made the time to clean up the class analyzer tool to be more generic 
(as its initial versions used to be) and add the incremental modules 
build support.  This is very close to the version that you reviewed some 
time ago [1].

Webrev at:
    http://cr.openjdk.java.net/~mchung/jigsaw/incremental-build/

The modules build includes three main steps:
a. run the class analyzer tool to assign classes and resources in the 
jdk modules and analyzes their dependencies
b. compile the module-info.java source files generated by the class analyzer
c. modularize the jdk build
     - copy classes, resources and other non-java files for each module 
to $OUTPUTDIR/modules/<m> directory where <m> is the module name
     - create the jigsaw module library and install the jdk modules in it.

To support the incremental build, the tools and makefile will need to 
detect what files and modules are modified.  To simplify the change, one 
single marker file is added and updated when any part of the jdk is 
remade.  The modules build will use the timestamp of the marker file to 
determine if it should do an incremental or do a full modules build.

I created a new tool com.sun.classanalyzer.Modularizer to do the 
timestamp comparison and the files copying.   Both ClassAnalyzer and 
Modularizer will process classes/resources files that are updated since 
the last build.

Thanks
Mandy

[1] 
http://mail.openjdk.java.net/pipermail/core-libs-dev/2010-July/004543.html