floatformat.h: Wrap in extern "C"

Just like libiberty.h.  So that C++ programs, such as GDB when built
as a C++ program, can use it.

include/ChangeLog:
2015-02-19  Pedro Alves  <palves@redhat.com>

	* floatformat.h [__cplusplus]: Wrap in extern "C".

From-SVN: r220812

include/ChangeLog

+2015-02-19  Pedro Alves  <palves@redhat.com>
+
+	* floatformat.h [__cplusplus]: Wrap in extern "C".
+
 2015-02-04  Jakub Jelinek  <jakub@redhat.com>
 
 	* dwarf2.h (enum dwarf_source_language): Add DW_LANG_Fortran03

include/floatformat.h

@@ -23,6 +23,10 @@ Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.
 
 #include "ansidecl.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* A floatformat consists of a sign bit, an exponent and a mantissa.  Once the
    bytes are concatenated according to the byteorder flag, then each of those
    fields is contiguous.  We number the bits with 0 being the most significant
@@ -149,4 +153,8 @@ floatformat_from_double (const struct floatformat *, const double *, void *);
 extern int
 floatformat_is_valid (const struct floatformat *fmt, const void *from);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif	/* defined (FLOATFORMAT_H) */