Pure storage removal: Remove support for pinned objects

Pure storage removal: Remove support for pinned objects

* src/alloc.c (symbol_block_pinned): Remove variable.
(init_symbol): Don't initialize 'pinned flag'.
(pinned_objects): Remove variable.
(mark_pinned_objects, mark_pinned_symbols): Remove functions.
(garbage_collect): Don't call 'mark_pinned_objects',
'mark_pinned_symbols'.
* src/lisp.h (struct Lisp_Symbol): Remove 'pinned' flag.
* src/pdumper.c (dump_symbol): Remove 'pinned' flag from dump.

(cherry picked from commit e1e101c6c10b6e5110c2c47946d477a752828a78)