* harbour/include/hbapifs.h
* harbour/source/rtl/filebuf.c
+ added hb_fileExists() and hb_fileDelete() functions
+ added support for alternative file IO API used in RDD code which
can be implemented by 3-rd party developers and registered using
hb_fileRegister() function.
* harbour/source/rdd/dbf1.c
* harbour/source/rdd/dbffpt/dbffpt1.c
* harbour/source/rdd/dbfntx/dbfntx1.c
* harbour/source/rdd/dbfnsx/dbfnsx1.c
* harbour/source/rdd/dbfcdx/dbfcdx1.c
* use hb_fileExist() and hb_fileDelete() functions for files accessed
by hb_file*() API
9bbf25760e