gnu: Rely on 'file' implicit input and 'patch-usr-bin-file'.

* gnu/packages/admin.scm (sudo):
* gnu/packages/gawk.scm (gawk): Remove workaround on MIPS.

* gnu/packages/mcrypt.scm (mcrypt, libmhash):
* gnu/packages/file.scm (file): Remove 'file' from native-inputs.

* gnu/packages/mc.scm (mc):
* gnu/packages/pretty-print.scm (a2ps, trueprint, source-highlight):
* gnu/packages/image.scm (libtiff): Remove 'file' from native-inputs.
  Remove 'patch-configure' phase.