[ELF2] Add mandatory .dynamic section entries on MIPS.

The MIPS target requires specific dynamic section entries to be defined.

 * DT_MIPS_RLD_VERSION and DT_MIPS_FLAGS store predefined values.
 * DT_MIPS_BASE_ADDRESS holds base VA.
 * DT_MIPS_LOCAL_GOTNO holds the number of local GOT entries.
 * DT_MIPS_SYMTABNO holds the number of .dynsym entries.
 * DT_MIPS_GOTSYM holds the index of the .dynsym entry
   which corresponds to the first entry of the global part of GOT.
 * DT_MIPS_RLD_MAP holds the address of the reserved space in the data segment.
 * DT_MIPS_PLTGOT points to the .got.plt section if it exists.
 * DT_PLTGOT holds the address of the GOT section.

See "Dynamic Section" in Chapter 5 in the following document for detailed
description: ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf

Differential revision: http://reviews.llvm.org/D14450

llvm-svn: 252857