Test gdb.base/reread.exp fails and reports ERROR for uClinux because it
renames binary files directly using "shell mv", and this doesn't take
into account the pair of binaries that are used for the bFLT format.

This patch moves the file commands into new procedures in lib/gdb.exp
that are used as defaults if the local environment doesn't override
them.

Tested on arm-none-linux-gnueabi as a platform that does not need
overrides.  OK?  I have an FSF copyright assignment for gdb.

Janis Johnson
CodeSourcery / Mentor Graphics