The vim-mkbuild plugin has been improved. It supports two diferent file
search sources for Unite!
* <leader>E maps to unite using the mkbuild/file source, which provides
all files in the project, including other projects referenced
externally in the optional extrefs file.
* <leader>e maps to unite using the mkbuild/file_xref source, which
provides that subset of files used in a specific mkbuild build. This
version requires the use of <leader>x first to set a build. If no
build is available, mkbuild/file_xref instead works just like
mkbuild/file.