[opaque pointer type] Add textual IR support for explicit type parameter to load instruction

Essentially the same as the GEP change in r230786.

A similar migration script can be used to update test cases, though a few more
test case improvements/changes were required this time around: (r229269-r229278)

import fileinput
import sys
import re

pat = re.compile(r"((?:=|:|^)\s*load (?:atomic )?(?:volatile )?(.*?))(| addrspace\(\d+\) *)\*($| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$)")

for line in sys.stdin:
  sys.stdout.write(re.sub(pat, r"\1, \2\3*\4", line))

Reviewers: rafael, dexonsmith, grosser

Differential Revision: http://reviews.llvm.org/D7649

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230794 91177308-0d34-0410-b5e6-96231b3b80d8

test/DebugInfo/missing-abstract-variable.ll

@@ -112,7 +112,7 @@ entry:
   br i1 %u, label %if.then.i, label %_Z1xb.exit, !dbg !34
 
 if.then.i:                                        ; preds = %entry
-  %0 = load i32* @t, align 4, !dbg !35, !tbaa !36
+  %0 = load i32, i32* @t, align 4, !dbg !35, !tbaa !36
   tail call void @llvm.dbg.value(metadata i32 %0, i64 0, metadata !40, metadata !{!"0x102"}), !dbg !35
   tail call void @_Z1fi(i32 %0), !dbg !41
   br label %_Z1xb.exit, !dbg !42