De-C++ where possible

Helps with avoiding many "extern C" declarations in source files.
diff --git a/src/Makefile.am b/src/Makefile.am
index ace7686..a8ba69c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -16,7 +16,7 @@
 	hb-buffer-private.hh \
 	hb-common.c \
 	hb-font.cc \
-	hb-font-private.hh \
+	hb-font-private.h \
 	hb-object-private.h \
 	hb-open-file-private.hh \
 	hb-open-type-private.hh \
@@ -82,7 +82,7 @@
 HBCFLAGS += $(FREETYPE_CFLAGS)
 HBLIBS   += $(FREETYPE_LIBS)
 HBSOURCES += \
-	hb-ft.cc \
+	hb-ft.c \
 	$(NULL)
 HBHEADERS += \
 	hb-ft.h \
diff --git a/src/check-header-guards.sh b/src/check-header-guards.sh
index b84fd68..59c399a 100755
--- a/src/check-header-guards.sh
+++ b/src/check-header-guards.sh
@@ -10,7 +10,7 @@
 
 for x in *.h *.hh ; do
 	tag=`echo "$x" | tr 'a-z.-' 'A-Z_'`
-	lines=`grep "$tag" "$x" | wc -l`
+	lines=`grep "\<$tag\>" "$x" | wc -l`
 	if test "x$lines" != x3; then
 		echo "Ouch, header file $x does not have correct preprocessor guards"
 		stat=1
diff --git a/src/hb-font-private.hh b/src/hb-font-private.h
similarity index 95%
rename from src/hb-font-private.hh
rename to src/hb-font-private.h
index 35aa4d5..7f54cbd 100644
--- a/src/hb-font-private.hh
+++ b/src/hb-font-private.h
@@ -24,8 +24,8 @@
  * Red Hat Author(s): Behdad Esfahbod
  */
 
-#ifndef HB_FONT_PRIVATE_HH
-#define HB_FONT_PRIVATE_HH
+#ifndef HB_FONT_PRIVATE_H
+#define HB_FONT_PRIVATE_H
 
 #include "hb-private.h"
 
@@ -92,4 +92,4 @@
 
 HB_END_DECLS
 
-#endif /* HB_FONT_PRIVATE_HH */
+#endif /* HB_FONT_PRIVATE_H */
diff --git a/src/hb-font.cc b/src/hb-font.cc
index 34c2345..8c4a608 100644
--- a/src/hb-font.cc
+++ b/src/hb-font.cc
@@ -26,7 +26,7 @@
 
 #include "hb-private.h"
 
-#include "hb-font-private.hh"
+#include "hb-font-private.h"
 #include "hb-blob-private.h"
 #include "hb-open-file-private.hh"
 
diff --git a/src/hb-ft.cc b/src/hb-ft.c
similarity index 99%
rename from src/hb-ft.cc
rename to src/hb-ft.c
index aee64f6..bdf2936 100644
--- a/src/hb-ft.cc
+++ b/src/hb-ft.c
@@ -29,7 +29,7 @@
 
 #include "hb-ft.h"
 
-#include "hb-font-private.hh"
+#include "hb-font-private.h"
 
 #include FT_TRUETYPE_TABLES_H
 
diff --git a/src/hb-graphite.cc b/src/hb-graphite.cc
index 54a01fc..8794db7 100644
--- a/src/hb-graphite.cc
+++ b/src/hb-graphite.cc
@@ -29,7 +29,7 @@
 #include <graphite/GrConstants.h>
 #include <graphite/Segment.h>
 #include "hb-buffer-private.hh"
-#include "hb-font-private.hh"
+#include "hb-font-private.h"
 #include "hb-graphite.h"
 #include <map>
 
diff --git a/src/hb-ot-layout-gdef-private.hh b/src/hb-ot-layout-gdef-private.hh
index 1adff6e..2f77ef4 100644
--- a/src/hb-ot-layout-gdef-private.hh
+++ b/src/hb-ot-layout-gdef-private.hh
@@ -29,7 +29,7 @@
 
 #include "hb-ot-layout-common-private.hh"
 
-#include "hb-font-private.hh"
+#include "hb-font-private.h"
 
 
 /*
diff --git a/src/hb-ot-layout-private.hh b/src/hb-ot-layout-private.hh
index decc8f7..8d0d469 100644
--- a/src/hb-ot-layout-private.hh
+++ b/src/hb-ot-layout-private.hh
@@ -32,7 +32,7 @@
 #include "hb-ot-layout.h"
 #include "hb-ot-head-private.hh"
 
-#include "hb-font-private.hh"
+#include "hb-font-private.h"
 #include "hb-buffer-private.hh"