Darwin: Add assembler directives to create version-min load commands.

Allow object files to be tagged with a version-min load command for iOS
or MacOSX.

Teach macho-dump to understand the version-min load commands for
testcases.

rdar://11337778

llvm-svn: 204190
diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index 89d7d19..910295c 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -296,6 +296,7 @@
   : Context(Context_), Backend(Backend_), Emitter(Emitter_), Writer(Writer_),
     OS(OS_), BundleAlignSize(0), RelaxAll(false), NoExecStack(false),
     SubsectionsViaSymbols(false), ELFHeaderEFlags(0) {
+  VersionMinInfo.Major = 0; // Major version == 0 for "none specified"
 }
 
 MCAssembler::~MCAssembler() {