Fix some "long double" nonsense

Apparently in addition to "float", "double" and "long double" there
are now standard types in <math.h> called "float_t" and "double_t".
Those types don't need to be equivalent to "float" and "double". Gah!

c/equalhash.c

@@ -1,5 +1,6 @@
 #include <assert.h>
 #include <limits.h>
+#include <math.h>
 #include <setjmp.h>
 #include <stdarg.h>
 #include <stdint.h>

c/flisp.h

@@ -353,8 +353,8 @@ struct fltype *get_array_type(value_t eltype);
 struct fltype *define_opaque_type(value_t sym, size_t sz,
                                   struct cvtable *vtab, cvinitfunc_t init);
 
-value_t mk_double(double n);
-value_t mk_float(float n);
+value_t mk_double(double_t n);
+value_t mk_float(float_t n);
 value_t mk_uint32(uint32_t n);
 value_t mk_uint64(uint64_t n);
 value_t mk_wchar(int32_t n);

c/flmain.c

@@ -1,4 +1,5 @@
 #include <assert.h>
+#include <math.h>
 #include <setjmp.h>
 #include <stdarg.h>
 #include <stdint.h>