[llvm-readobj][yaml2obj] Support SHT_LLVM_SYMPART, SHT_LLVM_PART_EHDR and SHT_LLVM_PART_PHDR

See http://lists.llvm.org/pipermail/llvm-dev/2019-February/130583.html
and D60242 for the lld partition feature.

This patch:

* Teaches yaml2obj to parse the 3 section types.
* Teaches llvm-readobj/llvm-readelf to dump the 3 section types.

There is no test for SHT_LLVM_DEPENDENT_LIBRARIES in llvm-readobj. Add
it as well.

Reviewed By: thakis

Differential Revision: https://reviews.llvm.org/D67228

llvm-svn: 371157
diff --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cpp
index 8660b1a..d491288 100644
--- a/llvm/lib/Object/ELF.cpp
+++ b/llvm/lib/Object/ELF.cpp
@@ -255,6 +255,8 @@
     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ADDRSIG);
     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_DEPENDENT_LIBRARIES);
     STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_SYMPART);
+    STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_PART_EHDR);
+    STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_PART_PHDR);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef);