Revert "allow lambdas in mapped_iterator"

MSVC as usual:

C:\Buildbot\Slave\llvm-clang-lld-x86_64-scei-ps4-windows10pro-fast\llvm.src\include\llvm/ADT/STLExtras.h(120):
error C2100: illegal indirection
C:\Buildbot\Slave\llvm-clang-lld-x86_64-scei-ps4-windows10pro-fast\llvm.src\include\llvm/IR/Instructions.h(3966):
note: see reference to class template instantiation
'llvm::mapped_iterator<llvm::User::op_iterator,llvm::CatchSwitchInst::DerefFnTy>'
being compiled

This reverts commit e091dd63f1f34e043748e28ad160d3bc17731168.

llvm-svn: 263760