mg_dtoa, mg_atod, mg_lld made static

src/fmt.h

@@ -7,10 +7,6 @@ typedef void (*mg_pfn_t)(char, void *);                  // Custom putchar
 typedef size_t (*mg_pm_t)(mg_pfn_t, void *, va_list *);  // %M printer
 void mg_pfn_iobuf(char ch, void *param);                 // iobuf printer
 
-size_t mg_lld(char *buf, int64_t val, bool is_signed, bool is_hex);
-double mg_atod(const char *buf, int len, int *numlen);
-size_t mg_dtoa(char *buf, size_t len, double d, int width);
-
 size_t mg_vxprintf(void (*)(char, void *), void *, const char *fmt, va_list *);
 size_t mg_xprintf(void (*fn)(char, void *), void *, const char *fmt, ...);
 size_t mg_vsnprintf(char *buf, size_t len, const char *fmt, va_list *ap);