Handle T_FLTCPLX in NewSwigType()

This fixes an assertion failure and segfault trying to use %constant
to deduce the type of a "float _Complex" constant.

Examples/test-suite/ccomplextest.i

@@ -26,6 +26,11 @@
 #endif
 %}
 
+%inline %{
+static float _Complex CPLX_CONSTANT_ = 0;
+%}
+%constant CPLX_CONSTANT = CPLX_CONSTANT_;
+
 %inline
 {
   int has_c99_complex(void) {

Source/Swig/stype.c

@@ -131,6 +131,8 @@ SwigType *NewSwigType(int t) {
     return NewString("double");
   case T_LONGDOUBLE:
     return NewString("long double");
+  case T_FLTCPLX:
+    return NewString("float _Complex");
   case T_COMPLEX:
     return NewString("_Complex");
   case T_CHAR: