Add file include/share/compat.h and start moving CPP hackery into it.

include/share/compat.h

@@ -0,0 +1,61 @@
+/* libFLAC - Free Lossless Audio Codec library
+ * Copyright (C) 2012  Xiph.org Foundation
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of the Xiph.org Foundation nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* This is the prefered location of all CPP hackery to make $random_compiler
+ * work like something approaching a C99 (or maybe more accurately GNU99)
+ * compiler.
+ *
+ * It is assumed that this header will be included after "config.h".
+ */
+
+#if defined _WIN32 && !defined __CYGWIN__
+/* where MSVC puts unlink() */
+# include <io.h>
+#else
+# include <unistd.h>
+#endif
+
+#if defined _MSC_VER || defined __BORLANDC__ || defined __MINGW32__
+#include <sys/types.h> /* for off_t */
+#if _MSC_VER <= 1600 || defined __BORLANDC__ /* @@@ [2G limit] */
+#ifndef fseeko
+#define fseeko fseek
+#endif
+#ifndef ftello
+#define ftello ftell
+#endif
+#endif
+#endif
+
+#if HAVE_INTTYPES_H
+#include <inttypes.h>
+#endif
+