[MCOMPILER-485] Fixes internal string format in generated package-info.class

[dbwiddis]

https://issues.apache.org/jira/browse/MCOMPILER-485

Per JVMS 4.2.1, the package name representation in the internal class structure always contains forward slashes in place of periods. This PR fixes the code from MCOMPILER-205 which passed a package name extracted from the file path which used backward slashes on Windows.

While not necessarily a cause of the bug, the javadocs for ClassVisitor (the superclass of ClassWriter) state "The methods of this class must be called in the following order: visit visitSource ..." so I reordered those method calls as well.

The IT is copied from MCOMPILER-205 but with a more detailed test to confirm the correct internal representation of the package name in the class file.

mvn -Prun-its clean verify after the first (IT) commit finds the failure; note the 5c (\) on windows vs. 2f (/).

Running post-build script: C:\Users\dawiddis.REDMOND\git\maven-compiler-plugin\target\it\MCOMPILER-485\verify.groovy
Assertion failed:

assert packageInfoHex.contains( '64756d6d792f7061636b6167652d696e666f' )
       |              |          d u m m y / p a c k a g e - i n f o 
       |              false
       cafebabe0000003400070100117061636b6167652d696e666f2e6a61766101001264756d6d795c7061636b6167652d696e666f0700020100106a61 ...
                                                                         d u m m y \ p a c k a g e - i n f o

After code fix, passes tests:

[INFO] Building: MCOMPILER-485\pom.xml
[INFO] run post-build script verify.groovy
[INFO]           MCOMPILER-485\pom.xml ............................ SUCCESS (3.0 s)

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[dbwiddis]

Sorry for the force-push churn. Finally got IT tests to work and had a upper/lower case issue in the hex string, then forgot to use fixup on the rebase. Should be good to go now.

[olamy]

Sorry for the force-push churn. Finally got IT tests to work and had a upper/lower case issue in the hex string, then forgot to use fixup on the rebase. Should be good to go now.

no worries mate. Thanks again for your help.

[olamy]

LGTM
maybe @gnodet could have a look as well?
thanks!