Add procfs_find_LDT_entry declaration (procfs.h).

Add a declaration for procfs_find_LDT_entry in order to prevent
a compiler warning about this function missing one. This also
helps making sure that declaration and definition remain consistent.

gdb/ChangeLog:

        * procfs.h (procfs_find_LDT_entry): Add declaration.
        * sol-thread.c (ps_lgetLDT): Delete local declaration of
        function procfs_find_LDT_entry.

gdb/sol-thread.c

@@ -1108,7 +1108,6 @@ ps_lgetLDT (gdb_ps_prochandle_t ph, lwpid_t lwpid,
 	    struct ssd *pldt)
 {
   /* NOTE: only used on Solaris, therefore OK to refer to procfs.c.  */
-  extern struct ssd *procfs_find_LDT_entry (ptid_t);
   struct ssd *ret;
 
   /* FIXME: can't I get the process ID from the prochandle or