Also, I had both clang 3.6 and 3.7 installed, but though I
installed 3.7 after 3.6, it was not set up as the default
version of clang. Then I removed 3.6 and there was no default
version of clang (I still had to use clang-3.7 and clang++-3.7
to invoke them). Is there a proper way to set up 3.7 as the
default version on Debian?