Add long_call attribute to mips port.

Add long_call attribute to mips port.

* config/mips/mips.c (mips_encode_section_info, mips_attribute_table,
TARGET_ENCODE_SECTION_INFO, TARGET_ATTRIBUTE_TABLE): New.
* config/mips/mips.h (SYMBOL_FLAG_LONG_CALL, SYMBOL_REF_LONG_CALL_P):
New.
* config/mips/predicates.md (const_call_insn_operand): Add check for
SYMBOL_REF_LONG_CALL_P.
* doc/extend.texi (long_call): Document the new attribute.

From-SVN: r102646