BUILDING.md: Added a new section about incremental compiling and a sentence about cleaning after switching branches.

This information is derived from a comment by mkristian:
https://github.com/jruby/jruby/issues/1470#issuecomment-33900740
Merge pull request #1475 from DavidEGrayson/building_pull_request

BUILDING.md: Added info about incremental compiling, cleaning after switching branches

[skip ci]
Bugfix for issue #1248

Change LoadService to cope with classpath entries containing spaces.  This
doesn't normally happen when JRuby is invoked from the command-line, but seems
to happen when running via jruby-rack.
Merge pull request #1477 from marktriggs/issue-1248

Bugfix for issue #1248
fix dependency [skip ci]
added IT for https://github.com/jruby/jruby/issues/1477

[skip ci]
fix dependency again [skip ci]
Removed the custom glob code and added "defacto" expectations
Merge
Now that regular file globbing handles jar entries well, no need for special parsing logic
Fix bad test which was using incorrect line 2 for a syntax error on line 1 and correct RubyWarnings to add 1 to position.getStartLine because it is zero based
Merge with jruby-1_7