Fix installation of LLVM codegen's RTS to incorrect path

Breakage introduced by c7cf1f0f
Test LLVM codegen on travis to reduce future breakage
Keep track of prototyped foreign symbols across definitions
Print failed pattern match error messages to stderr
Verify that foreign symbols declared in multiple places have a consistent signature
Merge pull request #523 from Ralith/fix-llvm-install

LLVM-related fixes