Added ability to call winapi_check from the Makefiles.

diff --git a/Make.rules.in b/Make.rules.in
index 91c3160..b1f0616 100644
--- a/Make.rules.in
+++ b/Make.rules.in
@@ -50,6 +50,7 @@
 LINT      = @LINT@
 LINTFLAGS = @LINTFLAGS@
 ALLLINTFLAGS = $(LINTFLAGS) $(DEFS) $(OPTIONS) $(DIVINCL)
+WINAPI_CHECK = $(TOPSRCDIR)/tools/winapi_check/winapi_check
 BUILD     = $(TOPOBJDIR)/tools/build@PROGEXT@
 MAKEDEP   = $(TOPOBJDIR)/tools/makedep@PROGEXT@
 WINERC    = $(TOPOBJDIR)/rc/winerc@PROGEXT@
@@ -172,6 +173,11 @@
 
 lint:: $(MODULE).ln
 
+# Rules for Windows API checking
+
+winapi_check::
+	$(WINAPI_CHECK) $(WINAPI_CHECK_FLAGS) $(WINAPI_CHECK_EXTRA_FLAGS) .
+
 # Misc. rules
 
 $(SPEC_SRCS:.spec=.spec.c): $(BUILD) $(TOPSRCDIR)/include/builtin16.h $(TOPSRCDIR)/include/builtin32.h