gdbsupport: move fast_hash to gdbsupport/common-utils.h

The following patch adds a hash type for gdb::string_view in gdbsupport,
which will use the fast_hash function.  Move the latter to gdbsupport.

Change-Id: Id74510e17801e775bd5ffa5f443713d79adf14ad
Approved-By: Andrew Burgess <aburgess@redhat.com>
2 files changed