Fix make check

The inline functions in cairo-backend-private.h tried to dereference a cairo_t,
which wasn't defined. Fix this by including cairo-private.h.

In cairo-mempool-private.h, size_t is used but stddef.h is not included.

Fixes:

  CHECK cairo-backend-private.h
In file included from headers-standalone-tmp.c:1:0:
./cairo-backend-private.h: In function ‘_cairo_backend_to_user’:
./cairo-backend-private.h:179:7: error: dereferencing pointer to incomplete type
./cairo-backend-private.h: In function ‘_cairo_backend_to_user_distance’:
./cairo-backend-private.h:185:7: error: dereferencing pointer to incomplete type
./cairo-backend-private.h: In function ‘_cairo_user_to_backend’:
./cairo-backend-private.h:191:7: error: dereferencing pointer to incomplete type
./cairo-backend-private.h: In function ‘_cairo_user_to_backend_distance’:
./cairo-backend-private.h:197:7: error: dereferencing pointer to incomplete type
  CHECK cairo-mempool-private.h
In file included from headers-standalone-tmp.c:1:0:
./cairo-mempool-private.h:61:5: error: unknown type name ‘size_t’
./cairo-mempool-private.h:62:5: error: unknown type name ‘size_t’
./cairo-mempool-private.h:68:8: error: unknown type name ‘size_t’
./cairo-mempool-private.h:73:44: error: unknown type name ‘size_t’

Signed-off-by: Uli Schlachter <psychon@znc.in>

src/cairo-backend-private.h

@@ -37,6 +37,7 @@
 #define CAIRO_BACKEND_PRIVATE_H
 
 #include "cairo-types-private.h"
+#include "cairo-private.h"
 
 typedef enum _cairo_backend_type {
     CAIRO_TYPE_DEFAULT,

src/cairo-mempool-private.h

@@ -40,6 +40,8 @@
 #include "cairo-compiler-private.h"
 #include "cairo-error-private.h"
 
+#include <stddef.h> /* for size_t */
+
 CAIRO_BEGIN_DECLS
 
 typedef struct _cairo_mempool cairo_mempool_t;