[macho] Minor install_name fixes

Summary:
Fix the binary file reader to properly read dyld version info.
Update the install_name test case to properly test the binary reader. We can't use '-print_atoms' as the output format is 'native' yaml and it does not contains the dyld current and compatibility versions. 

Also change the timestamp value of LD_ID_DYLD to match the one generated by ld64.
The dynamic linker (dyld) used to expects different values for timestamp in LD_ID_DYLD and LD_LOAD_DYLD for prebound images. While prebinding is deprecated, we should probably keep it safe and match ld64. 

Reviewers: kledzik

Subscribers: llvm-commits

Projects: #lld

Differential Revision: http://reviews.llvm.org/D6736

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@224681 91177308-0d34-0410-b5e6-96231b3b80d8