Fix warnings

This change fixes Cosmopolitan so it has fewer opinions about compiler
warnings. The whole repository had to be cleaned up to be buildable in
-Werror -Wall mode. This lets us benefit from things like strict const
checking. Some actual bugs might have been caught too.

third_party/gdtoa/gdtoa_fltrnds.inc

@@ -1,7 +1,8 @@
 /* clang-format off */
 
-	FPI *fpi, fpi1;
+	FPI fpi1;
 	int Rounding;
+	const FPI *fpi;
 	Rounding = FLT_ROUNDS;
 	fpi = &fpi0;
 	if (Rounding != FPI_Round_near) {

third_party/gdtoa/misc.c

@@ -128,7 +128,6 @@ __gdtoa_Balloc(int k, ThInfo **PTI)
 {
 	int x;
 	Bigint *rv;
-	unsigned int len;
 	ThInfo *TI;
 	if (!(TI = *PTI))
 		*PTI = TI = __gdtoa_get_TI();

third_party/gdtoa/strtord.c

@@ -67,7 +67,8 @@ int
 strtord(const char *s, char **sp, int rounding, double *d)
 {
 	static const FPI fpi0 = { 53, 1-1023-53+1, 2046-1023-53+1, 1, SI, 0 /*unused*/ };
-	FPI *fpi, fpi1;
+	FPI fpi1;
+	const FPI *fpi;
 	ULong bits[2];
 	Long exp;
 	int k;

third_party/gdtoa/strtordd.c

@@ -165,7 +165,8 @@ int
 strtordd(const char *s, char **sp, int rounding, double *dd)
 {
 	static const FPI fpi0 = { 106, 1-1023-53+1, 2046-1023-106+1, 1, 0, 0 /*unused*/ };
-	FPI *fpi, fpi1;
+	FPI fpi1;
+	const FPI *fpi;
 	ULong bits[4];
 	Long exp;
 	int k;

third_party/gdtoa/strtorf.c

@@ -63,7 +63,8 @@ int
 strtorf(const char *s, char **sp, int rounding, float *f)
 {
 	static const FPI fpi0 = { 24, 1-127-24+1,  254-127-24+1, 1, SI, 0 /*unused*/ };
-	FPI *fpi, fpi1;
+	FPI fpi1;
+	const FPI *fpi;
 	ULong bits[1];
 	Long exp;
 	int k;

third_party/gdtoa/strtorx.c

@@ -74,7 +74,8 @@ int
 strtorx(const char *s, char **sp, int rounding, void *L)
 {
 	static const FPI fpi0 = { 64, 1-16383-64+1, 32766 - 16383 - 64 + 1, 1, SI, 0 /*unused*/ };
-	FPI *fpi, fpi1;
+	FPI fpi1;
+	const FPI *fpi;
 	ULong bits[2];
 	Long exp;
 	int k;