Fix libgcc build failed by ABI mismatch.
Update the source archive to 4.6.4-20140516.
Add patch from https://gcc.gnu.org/bugzilla/attachment.cgi?id=28797 .
Add --enable-obsolete to configure script.
Add patch for nios2-elf.
Comment out targets except pf-gnuchains4x-nios2-elf.
Revert "Comment out targets except pf-gnuchains4x-nios2-elf."

This reverts commit af0fccb3c56be5a044a592175ce5631ab34cf4a9.
Merge branch 'release/release-1.0.0'