Fill 0 for negative decimals if precision is given

If precision is given for negative decimals, fill in 0's as necessary.
This fixes #936.
account only for significant digits in ConvertDouble
do not quit parseExponent() early, just break out of loop
Update to joda-time 2.3 (and tzdata 2013d)

$ jruby -ve 'require "rbconfig";
puts RbConfig::CONFIG["joda-time.version"];
puts RbConfig::CONFIG["tzdata.version"]'
jruby 1.7.5.dev (1.9.3p392) 2013-09-02 ba28553 on Java HotSpot(TM) 64-Bit Server VM 1.7.0_25-b15 [darwin-x86_64]
2.3
2013d
Merge branch 'master' of jruby.org:jruby
Revert joda-timezones to 2013c

2013d is not available on maven repositories
Check 'frozen' and 'enclosed' before moving Thread

When moving a Thread from one ThreadGroup to another, both
the source and the target ThreadGroup must not be frozen or enclosed.

This fixes #950.
Fix regression spec on case-insensitive fs [skip ci]

When the file does not exist, it should raise LoadError.

Fixes https://github.com/jruby/jruby/issues/758
Update RubyGems to 2.0.7
Revert "Fix regression spec on case-insensitive fs [skip ci]"

This reverts commit db349bd7aac4d10b43bd3dd1f7873bcdd10e4ffa.
Remove JRUBY-5811 regression spec

Case-insensitive `LOADED_FEATURES` scanning is abandoned (65c07ea).

Fixes #758.
Merge branch 'master' into rubygems-2.0.7
Update tzdata to 2013d
Merge branch 'rubygems-2.0.7'
Use snapshot of joda-timezones artifact in transition to release.