bug#33548: 25.1; GUD GDB doesn't decode file paths correctly

[ksqsf]

Dear maintainers,

It seems that GDB MI doesn't decode file paths correctly, which can
result in some really weird unexpected behaviors.

For example, it attempts to find file
/home/ksqsf/我的坚果云/"/home/ksqsf/\346\210\221\347\232\204\345\235\232\346
\236\234\344\272\221/code.cpp"

I traced down to the source and found that gdb-get-source-file, gdb-
get-source-file-list, and gdb-get-location don't decode file paths
using a correct coding system. (In my case, UTF-8.) Instead, they
simply use 'read'.

Hope this can be fixed soon!

Regards,
_rika