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.

dsp/tty/rgb2ansi.c

@@ -98,8 +98,8 @@ static int uncube(int x) {
 }
 
 static textstartup void rgb2ansi_init(void) {
-  uint8_t c, y;
-  uint32_t i, j;
+  uint8_t c;
+  uint32_t i;
   memcpy(g_ansi2rgb_, &kCgaPalette, sizeof(kCgaPalette));
   for (i = 16; i < 232; ++i) {
     g_ansi2rgb_[i].r = kXtermCube[((i - 020) / 044) % 06];

dsp/tty/ttyraster.c

@@ -609,7 +609,7 @@ static struct Pick PickBlockUnicodeAnsi(struct TtyRgb tl, struct TtyRgb tr,
   struct TtyRgb tr2 = GetQuant(tr);
   struct TtyRgb bl2 = GetQuant(bl);
   struct TtyRgb br2 = GetQuant(br);
-  unsigned i, p1, p2;
+  unsigned p1, p2;
   uint16_t picks1[96] forcealign(32);
   uint16_t picks2[32] forcealign(32);
   memset(picks1, 0x79, sizeof(picks1));
@@ -646,7 +646,7 @@ static struct Pick PickBlockCp437Ansi(struct TtyRgb tl, struct TtyRgb tr,
   struct TtyRgb tr2 = GetQuant(tr);
   struct TtyRgb bl2 = GetQuant(bl);
   struct TtyRgb br2 = GetQuant(br);
-  unsigned i, p1, p2;
+  unsigned p1, p2;
   uint16_t picks1[32] forcealign(32);
   uint16_t picks2[32] forcealign(32);
   memset(picks1, 0x79, sizeof(picks1));
@@ -660,7 +660,6 @@ static struct Pick PickBlockCp437Ansi(struct TtyRgb tl, struct TtyRgb tr,
 
 static struct Pick PickBlockCp437True(struct TtyRgb tl, struct TtyRgb tr,
                                       struct TtyRgb bl, struct TtyRgb br) {
-  unsigned i;
   uint16_t picks[32] forcealign(32);
   memset(picks, 0x79, sizeof(picks));
   PickCp437(picks, tl, tr, bl, br, tl, tr, bl, br);

dsp/tty/write.c

@@ -38,8 +38,8 @@
  * @return 0 on success, or -1 w/ errno
  */
 ssize_t ttywrite(int fd, const void *data, size_t size) {
-  char *p;
   ssize_t rc;
+  const char *p;
   size_t wrote, n;
   p = data;
   n = size;