Scrap preprocessor, add .include directive instead

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

examples/constants.asm

@@ -0,0 +1,7 @@
+.section data $0x1000 {
+    dead: .u16 $0xDEAD
+    beef: .u16 $0xBEEF
+
+    .export dead
+    .export beef
+}