[docs][llvm-nm][llvm-objdump] Improve "See Also" section

The "See Also" section for llvm-nm didn't actually contain any links,
and the tools referred to didn't make much sense (referring to non-LLVM
tools, when we have equivalents, or tools that aren't really to do with
symbol dumping). llvm-objdump's didn't refer to llvm-readelf.

Reviewed by: grimar

Differential Revision: https://reviews.llvm.org/D63875

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@364552 91177308-0d34-0410-b5e6-96231b3b80d8

docs/CommandGuide/llvm-nm.rst

@@ -281,4 +281,5 @@ EXIT STATUS
 SEE ALSO
 --------
 
-llvm-dis, ar(1), nm(1)
+:manpage:`llvm-ar(1)`, :manpage:`llvm-objdump(1)`, :manpage:`llvm-readelf(1)`,
+:manpage:`llvm-readobj(1)`

docs/CommandGuide/llvm-objdump.rst

@@ -330,4 +330,4 @@ To report bugs, please visit <http://llvm.org/bugs/>.
 SEE ALSO
 --------
 
-:manpage:`llvm-nm(1)`, :manpage:`llvm-readobj(1)`
+:manpage:`llvm-nm(1)`, :manpage:`llvm-readelf(1)`, :manpage:`llvm-readobj(1)`