On the Command Guide page, there are multiple sections with links to the
different documentation pages available for LLVM tools. The "Basic
Tools" section includes tools like llvm-objdump, llvm-nm and so on. The
"Developer Tools" section contains things like FileCheck and lit. This
change moves llvm-readobj into the former block, from the latter.

Reviewed by: MaskRay

Differential Revision: https://reviews.llvm.org/D63011

llvm-svn: 362813