fixed issue 2050: add null check
Merge pull request #2123 from k77ch7/GH-2050

Fix for issue 2050 : BigDecimal and nil multiplication
Rework TZ parsing and marshal the Time zone

* Much less duplication for HHMM parsing.
* Stricter and clearer methods for getting a DateTimeZone.
* Fixes incorrect types for offset.
* Fixes #1837 and #957.

Conflicts:
	core/src/main/java/org/jruby/RubyTime.java
	test/mri/excludes/TestTime.rb
Update jzlib. Fixes 2169.
allow both "jar:file:./my.jar!/" and "jar:file:./my.jar!" as LOAD_PATH entries

this was a regression introduced with jruby-1.7.13 - fixes #2017

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newer versions of jnr-posix and joda-time
added tests for jruby-complete.jar

* travis just pick jdk7 to run those tests
* use uri:classloader://META-INF/jruby.home as jruby-home
* the antlib/extra.xml will be generated while generating the test/pom.xml from test/pom.rb
  and uses jruby19.index as source of test files (```cd test; rmvn validate```)
* the test-helper needed some improvements to accommodate jruby-complete
* jrubyc test is skipped since JRuby::Compiler.compile_argv only works with filebase jruby installations

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when testing File.file? the impl needs to use the FileResource.file?

the old implementation used FileResource.stat.file? which throws a
'File or Directory not found' and does no testing. the new implementation
follows the pattern used for File.directory? and File.exists?

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added tests for File.file? with native.enabled=false

complements the fix for #2032 with a test case for testing File.exists?,
File.directory? and File.file? executing jruby without native enabled.

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fix to obey 1.8 syntax
more tests for jruby-complete and alike

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[build] get finally all installed before running the tests
dealing with joda-time-2.5 ArithmeticException
fix another joda-2.5 exception

one exception I see only locally and the other I see only on travis - no idea why. treat both
as RangeError on the ruby side which honors the test-case.
do not run core/src/test/** test for the jruby-complete tests
[build] just get the test classes compiled but do not run the tests in core
fix null case and RubyHash when creating a new ConvertingMarshaller  - fixes #2120
Actually include filename in File.stat ENOENT error.
added mri.1.9 tests for jruby-complete

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added regular tests for jruby main maven artifact

some tests are not working and get omitted - https://github.com/jruby/jruby/issues/2215
and one test got a little workaround for https://github.com/jruby/jruby/issues/2216

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