Use switch for readability.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@206638 91177308-0d34-0410-b5e6-96231b3b80d8
Remove redundant "explicit" keywords.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@206639 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Add one more test for r206633.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@206645 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Support LIBRARY directive.

LIBRARY directive in a module definition file specifies the output
DLL file name. It also takes an optional value for the base address.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@206647 91177308-0d34-0410-b5e6-96231b3b80d8