Inline short member function.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@210086 91177308-0d34-0410-b5e6-96231b3b80d8
Fix build breakage.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@210087 91177308-0d34-0410-b5e6-96231b3b80d8
Rename FileToMutable -> SimpleFileWrapper.

FileToMutable is what this class does, but this class (or, to be precise,
an instance of this class) is a wrapper of the other SimpleFile. It's odd
that the class was named like a function.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@210089 91177308-0d34-0410-b5e6-96231b3b80d8
Improve error message.

Previously the parser always printed out an error message followed
by "Invalid file type" even if the file type is correct.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@210093 91177308-0d34-0410-b5e6-96231b3b80d8