* README: Remove claim that MEMORY is not supported.

    * README: Remove claim that MEMORY is not supported.
        * expression.cc (script_exp_function_origin)
        (script_exp_function_length): Move from here to ...
        * script.cc: ... here.
        (script_set_section_region, script_add_memory)
        (script_parse_memory_attr, script_include_directive): New
        functions.
        * script-sections.cc
        (class Memory_region): New class.
        (class Output_section_definition): Add set_memory_region,
        set_section_vma, set_section_lma and get_section_name methods.
        (class Script_Sections): Add add_memory_region,
        find_memory_region, find_memory_region_origin,
        find_memory_region_length and set_memory_region methods.
        Have set_section_addresses method walk the list of set memory
        regions.
        Extend the print methos to display memory regions.
        * script-sections.h: Add prototypes for new methods.
        Add enum for MEMORY region attributes.
        * yyscript.y: Add support for parsing MEMORY regions.
        * script-c.h: Add prototypes for new functions.
        * testsuite/Makefile.am: Add test of MEMORY region functionality.
        * testsuite/Makefile.in: Regenerate.
        * testsuite/memory_test.sh: New script.
        * testsuite/memory_test.s: New assembler source file.
        * testsuite/memory_test.t: New linker script.