preproc: add support for builtin include modules (%use)

Add a builtin equivalent to the %include directive called %use.
%use includes a standard macro file compiled into the binary; these
come from the macros/ directory in the source code.

The idea here is to be able to provide optional macro packages with
the distribution, without adding complex host filesystem dependencies.

1 files changed, 1 insertions, 0 deletions

diff --git a/pptok.dat b/pptok.dat
index 78a975fd..a30dd7e0 100644
--- a/pptok.dat
+++ b/pptok.dat
@@ -47,5 +47,6 @@
 %strlen
 %substr
 %undef
+%use
 %warning
 %xdefine