Add build.header.c

A new module type for creating just a header file. This is useful for e.g.
shared interfaces and so on which are not backed by a library.

scripts/build.header.c/build.monolithic

@@ -0,0 +1,16 @@
+# These are external variables, and shouldn't clash with anything else
+#  @CNAME@_MONOLITHIC
+
+HDR="obj/@HEADER_NAME@"
+
+MONOLITHIC_TESTS="src/@NAME@/build.monolithic"
+
+if [ -z "${@CNAME@_MONOLITHIC}" ]
+then
+    MONOLITHIC_SOURCE="$(find src/@NAME@/ -name '*.h' | sort)"
+    make_monolithic ${HDR} Ch || return 1
+
+    @CNAME@_MONOLITHIC=1
+    MONOLITHIC_DOC="${MONOLITHIC_DOC} ${HDR}"
+fi
+# vim: syntax=sh:@VIM_MODELINE@