Fix for Mantis #26278.

pbase.pas:
  + add an overload for identifier_not_found for which the file position can be supplied
pexpr.pas, factor_read_id:
  * store the file position before reading the identiifer token
  * use the new identiifer_not_found overload to explicitely set the file position
  * set the file position of the created node


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@27947 3ad0048d-3df7-0310-abae-a5850022a9f2