Merge branch 'develop'

* develop:
  Fix location of bootstrap log on Windows.
  Ignore build directories
  Fix mdash->emdash typo that broke documentation build.
Merge branch 'develop'

* develop:
  Make installation of Boost.Build work again.
Merge branch 'develop'
Merge branch 'develop'
Merge branch 'develop'
Fixed python 2to3 translation
Merge pull request #31 from dean0x7d/develop

Fixed python 2to3 translation
Python Port: Make importing a little more robust.

- create a b2.<whatever> index for O(1) package/module searching.
- make the .pyc's sit next to their respective files; preventing
  pollution of workspace
- restore the __file__ variable for imported files
- prevent importing the same module twice under two separate names;
  also preventing running initialization code twice (registering types
  and features)
- create an __init__.py for the contrib directory
- requires Python 2.3 or newer for pkgutil
Command in init should be a list, not a string
Use module name instead of Match instance for key of __module_flags.
Init params should be unique with requirements. Variable name shadowing.
Command param in init should be a list or handle when it is a string.
Second argmuent to type.register should be list. This registers the extensions t, l, and b instead of 'tlb'.
Prevent errors for double path separtors in PATH.
Port path.reverse().
Port regex.replace() and regex.replace_list().
Port asm.set_asm_type()
Merge pull request #35 from frenchtoast747/features/porting

Support for extra functions in Python port.

In particuar, path.reverse, regex.replace, regex.replace_list and asm.set_asm_type.
Merge pull request #33 from frenchtoast747/features/bug-fixes

Python Port: Bug fixes
Add get_target_variable to engine interface.