* config/m68hc11/m68hc11.c (m68hc11_handle_page0_attribute): New.
(m68hc11_attribute_table): New attribute "page0" to mark a global
variable as being allocated from within page0 section.
(m68hc11_encode_label): New function.
(m68hc11_strip_name_encoding): New function.
(m68hc11_page0_symbol_p): New function.
(m68hc11_indirect_p): Accept global variables marked in page0.
(m68hc11_encode_section_info): Lookup "page0" attribute.
* config/m68hc11/m68hc11.h (EXTRA_CONSTRAINT): 'R' constraint also
represents access to page0 variables.