Log Message:
Update to 5.2.1;  remove ONLY_FOR_PLATFORM: even though gdb is in the NetBSD
base system, people may want to install it from pkgsrc, particularly on
Darwin (?), Linux, SunOS and since there is no problem in having one gdb in
pkgsrc and one in the base-system, no harm is done.

Changes since the last version (4.18) are numerous; highlights include:
* New command "set trust-readonly-sections on[off]".
* New command "generate-core-file" (or "gcore").
* New command line option --pid or -p followed by a process id
* The new `--args' feature can be used to specify command-line arguments
  for the inferior from gdb's command line.
* a new `operate-and-get-next' function bound to `C-o'.