Make internal/private GVs implicitly dso_local.

While updating clang tests for having clang set dso_local I noticed
that:

- There are *a lot* of tests to update.
- Many of the updates are redundant.

They are redundant because a GV is "obviously dso_local". This patch
starts formalizing that a bit by requiring that internal and private
GVs be dso_local too. Since they all are, we don't have to print
dso_local to the textual representation, making it a bit more compact
and easier to read.

llvm-svn: 322317

llvm/test/Bitcode/thinlto-summary-section.ll

@@ -4,10 +4,10 @@
 ; RUN: llvm-lto -thinlto -o %t2 %t.o
 ; RUN: llvm-bcanalyzer -dump %t2.thinlto.bc | FileCheck %s --check-prefix=COMBINED
 
-; Flags should be 0x17 (23) for local linkage (0x3) and not being importable
+; Flags should be 0x57 (87) for local linkage (0x3), dso_local (0x40) and not being importable
 ; (0x10) due to local linkage plus having a section.
-; CHECK: <PERMODULE {{.*}} op1=23
-; COMBINED-DAG: <COMBINED {{.*}} op2=23
+; CHECK: <PERMODULE {{.*}} op1=87
+; COMBINED-DAG: <COMBINED {{.*}} op2=87
 define internal void @functionWithSection() section "some_section" {
     ret void
 }