RFR: 8039411 : Add environment variable support to fixpath

[Mike Duigou]

Hello all;

Currently the fixpath utility used in windows builds expects that the first parameter it is passed will be the path of the executable. In some cases it's desirable to define environment variables which will apply during the execution of that executable. This change adds support for defining environment variables. The variables appear before the executable. Currently the command line parsing assumes that all arguments containing "=" before the command path are environment variables. (This precludes the executable having '=' in it's path, which is unlikely anyway).

The remainder of the changes were lint warnings suggested by Visual C. (mostly const)

https://bugs.openjdk.java.net/browse/JDK-8039411
http://cr.openjdk.java.net/~mduigou/JDK-8039411/0/webrev/

Mike