Allow compilation of compiler with 2.6.x RTL for simplyfied development.

cfileutl.pas:
  + define a TRawByteSearchRec if we're not compiling with at least a 2.7.1 compiler


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25456 3ad0048d-3df7-0310-abae-a5850022a9f2