Make the "info dll" command available on all platform.

The "info dll", an alias of the "info sharedlibrary" command, is
currently only defined in windows native versions. This patch makes
it universally available by moving the alias declaration to solib.c,
and adjusts the documentation accordingly.

Making it universally available has two benefits:
  - Windows users moving to a Unix platforms are still able to use
    the same command for getting the list of shared libraries;
  - Unix to Windows cross debuggers now provide that command also.

gdb/ChangeLog:

        * solib.c (_initialize_solib): Add "info dll" alias creation.
        * windows-nat.c (set_windows_aliases): Delete.
        (_initialize_windows_nat): Remove deprecated_init_ui_hook
        assignment.
        * NEWS: Add news entry about "info dll" now being available
        on all platforms.

gdb/doc/ChangeLog:

        * gdb.texinfo (Files): Add "info dll" documentation.
        (Cygwin Native): Remove "info dll" documentation.

1 files changed, 3 insertions, 0 deletions

diff --git a/gdb/NEWS b/gdb/NEWS
index 651401d..0c7084a 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -23,6 +23,9 @@
   present in the debug info.  This typically includes the compiler version
   and may include things like its command line arguments.
 
+* The "info dll", an alias of the "info sharedlibrary" command,
+  is now available on all platforms.
+
 * Directory names supplied to the "set sysroot" commands may be
   prefixed with "target:" to tell GDB to access shared libraries from
   the target system, be it local or remote.  This replaces the prefix