[ELF] Sectionkey should also contain path.

No change in functionality.
[ELF] Rename MergedSection to OutputSection.

No change in functionality.
[ELF] Create input and output section names

No change in functionality.
[ELF] Fix creation of segments.

Linker was creating a separate output segment in some cases if input sections
had huge alignments. This patch fixes the issue.
[ELF] Handle ctors/dtors sections

Move functionality from MIPS target to DefaultLayout.

No change in functionality.