Remove macros from .gitattributes to avoid Git errors.

#1111224: Introduce .gitattributes to end the CRLF/LF and binary diff horror, and detect/auto-fix whitespace errors introduced a .gitattributes file into Drupal core. However, this file defines macros which are only allowed at the top-level of a repository. This prevents Drupal from being installed in a subdirectory of a larger repository without causing errors:

[attr]drupaltext    text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
 not allowed: drupal/.gitattributes:13
[attr]drupalbinary  -text diff
 not allowed: drupal/.gitattributes:18

Proposed solution: remove the macros and expand drupaltext and drupalbinary to include all the attributes in the macros. This sacrifices some loss in readability for portability.