Multiple trivial identical C programs. Each just includes Carbon.h,
which includes many of Apple's GUI headers.
After initial compile, subsequent files 3 times as fast
as without server.
Compiling a mix of medium-sized gcc,c
is over 30% faster using client+server.
Compiling 9 Tcl .c files yields similar speed-up.
Overhead of using server seems in the noise.
Actual numbers will depend on fraction of header-code re-use.
Numbers may get worse if we add more complete dependency checking.