Use internal dtoa/strtod for double conversion

The internal Lua CJSON dtoa/strtod routines have locale support
disabled. This avoids problems under locales with comma decimal
separators.

Build changes:
- CMake: Check for big endian architectures
- Makefile: Provide option to build with dtoa.c

Modifications to dtoa.c:
- Include locale dtoa_config.h configuration
- Rename Infinity/NaN to inf/nan to match common C libraries
- Rename strtod() -> internal_strtod() to prevent conflict with libc
  function

Modifications to g_fmt.c:
- Return output string length (instead of original buffer pointer)
- Provide precision as an argument to g_fmt()
- Silence compilations warnings from vendor source
  - while(a = b)
  - Unused label "done:"
- Only swap to scientific notation when once the number of decimal
  digits required exceeds the precision available. This matches
  standard printf format %g.
- Display a "0" in front of numbers < 1.

1 files changed, 9 insertions, 1 deletions

diff --git a/fpconv.h b/fpconv.h
index ea875c0..ac2f2c4 100644
--- a/fpconv.h
+++ b/fpconv.h
@@ -6,7 +6,15 @@
  * -1.7976931348623e+308 */
 # define FPCONV_G_FMT_BUFSIZE   32
 
-extern void fpconv_init();
+#ifdef USE_INTERNAL_DTOA
+static inline void fpconv_init()
+{
+    /* Do nothing - not required */
+}
+#else
+extern inline void fpconv_init();
+#endif
+
 extern int fpconv_g_fmt(char*, double, int);
 extern double fpconv_strtod(const char*, char**);