Bug#785697: clang-3.6: Clang++ does not find standard include files, e.g. <iostream>

[GSeifert]

Package: clang-3.6
Version: 1:3.6-2
Severity: normal

Dear Maintainer,

*** Reporter, please consider answering these questions, where appropriate ***

   * What led up to the situation?
   Latest apt-get update/apt-get upgrade/Installation of gcc-5 (I think)
   * What exactly did you do (or not do) that was effective (or
     ineffective)?
   Project, which compiled before the upgrade perfectly now bails out with "main.cpp:1:10: fatal error: 'iostream' file not found".
   gcc toolchain still works as expected.
   * What was the outcome of this action?
   "main.cpp:1:10: fatal error: 'iostream' file not found".


-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386, armel, armhf

Kernel: Linux 4.0.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to en_US.UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages clang-3.6 depends on:
ii  binutils                 2.25-7
ii  libc6                    2.19-18
ii  libc6-dev                2.19-18
ii  libclang-common-3.6-dev  1:3.6-2
ii  libclang1-3.6            1:3.6-2
ii  libedit2                 3.1-20150325-1
ii  libffi6                  3.1-2+b2
ii  libgcc-4.9-dev           4.9.2-17
ii  libgcc1                  1:5.1.1-5
ii  libllvm3.6               1:3.6-2
ii  libobjc-4.9-dev          4.9.2-17
ii  libstdc++-4.9-dev        4.9.2-17
ii  libstdc++6               5.1.1-5
ii  libtinfo5                5.9+20140913-1+b1
ii  zlib1g                   1:1.2.8.dfsg-2+b1

Versions of packages clang-3.6 recommends:
ii  llvm-3.6-dev  1:3.6-2
ii  python        2.7.9-1

Versions of packages clang-3.6 suggests:
pn  clang-3.6-doc  <none>
pn  gnustep        <none>
pn  gnustep-devel  <none>

-- no debconf information