Be consistent about using "const Twine &" for filenames.

On this file we had a mix of
* Twine
* const char *
* StringRef

The two that make sense are
* const Twine & (caller convenience)
* consc char * (that is what will eventually be passed to open.

Given that sys::fs::openFileForRead takes a "const Twine &", I picked that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219224 91177308-0d34-0410-b5e6-96231b3b80d8
Remove the IsVolatileSize parameter of getOpenFileSlice.

getOpenFileSlice gets passed the map size, so it makes no sense to say that
the size is volatile. The code will not even compute the size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219226 91177308-0d34-0410-b5e6-96231b3b80d8
llvm-readobj: add support to dump (COFF) directives

PE/COFF has a special section (.drectve) which can be used to pass options to
the linker (similar to LC_LINKER_OPTION).  Add support to llvm-readobj to print
the contents of the section for tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219228 91177308-0d34-0410-b5e6-96231b3b80d8
MC: add support for -aligncomm GNU extension

The GNU linker supports an -aligncomm directive that allows for power-of-2
alignment of common data.  Add support to emit this directive.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219229 91177308-0d34-0410-b5e6-96231b3b80d8