[dia] [clang-cl] Avoid redefinition of isnan and is isinf

[Hans Breuer <hans src gnome org>]

commit cd39f5e515d4e688b4bb74264f9d3f91309b9238
Author: Hans Breuer <hans breuer org>
Date:   Mon Dec 16 13:23:53 2013 +0100

    [clang-cl] Avoid redefinition of isnan and is isinf

 lib/geometry.h |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/lib/geometry.h b/lib/geometry.h
index 8229a08..13b49e5 100644
--- a/lib/geometry.h
+++ b/lib/geometry.h
@@ -37,7 +37,9 @@
 #include <ieeefp.h>
 #endif
 #ifndef HAVE_ISINF
-#define isinf(a) (!finite(a))
+#  ifndef isinf
+#    define isinf(a) (!finite(a))
+#  endif
 #endif
 
 #ifdef _MSC_VER 
@@ -45,7 +47,9 @@
    /* there are some things more in the gcc headers */
 #  include <float.h>
 #  define finite(a) _finite(a)
-#  define isnan(a) _isnan(a)
+#  ifndef isnan
+#    define isnan(a) _isnan(a)
+#  endif
 #endif
 #ifdef G_OS_WIN32
 #  define M_PI      3.14159265358979323846