Support for Clang plugins (still) not working in 3.1.9

 Hello,

 it looks like my patch 06be1c4cc33bf2def9c6e64483b397128f57dbe3 got included 
incorrectly into the maint branch.

 I don't know how exactly the maint branch works, I expect my patch didn't 
make it into 3.1.8 because you didn't want to include the patch from master 
that soon, but even though it's been included in 3.1.9, that ccache version 
still sees such compiles as 'multiple source files', because it requires 
8e005b067d8c2423e24ee14ffdee8343f650f1e8 too. Could you please include that 
commit as well? Thank you.

-- 
 Lubos Lunak
 [email protected]