[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/CodeGen/PowerPC/ppc64-byval-align.ll

@@ -31,7 +31,7 @@ entry:
 define i64 @callee2(%struct.pad* byval nocapture readnone %x, i32 signext %y, %struct.test* byval align 16 nocapture readonly %z) {
 entry:
   %x1 = getelementptr inbounds %struct.test, %struct.test* %z, i64 0, i32 0
-  %0 = load i64* %x1, align 16
+  %0 = load i64, i64* %x1, align 16
   ret i64 %0
 }
 ; CHECK-LABEL: @callee2