make the system path separator public

Hi, all.

I'm working on adding support for the CPATH, C_INCLUDE_PATH, etc environment
variables in clang. They hold lists of include directories, formatted like
the PATH environment variable: on Windows the separator is a semicolon, on
Unix the separator is a colon. It makes sense to me to have the llvm System
library export the separator, since it already knows what it is.

Doing this also allowed me to push the getPathList function up into the
shared System/Path code. (I considered exporting the getPathList function
itself, but the "include" environment variables treat empty entries in a
special way.)

I would appreciate someone merging this patch if there are no objections to it.

Sam Bishop

make-path-separator-public.patch (3.52 KB)

Looks great to me, thanks!