libc: Recompile newlib to enable float & long double i/o in printf/scanf

Enabled by default, set PRINTF_SCANF_FLOAT_SUPPORT=0 in local.mk/Makefile to disable

newlib-xtensa revision ae10be3

Configure/compile steps:

../configure --with-newlib --enable-multilib
--disable-newlib-io-c99-formats --enable-newlib-supplied-syscalls --enable-target-optspace --program-transform-name="s&^&xtensa-lx106-elf-&" --disable-option-checking --with-target-subdir=xtensa-lx106-elf
--target=xtensa-lx106-elf --prefix=/home/gus/dev/esp/rtos/open-rtos/libc/ --enable-newlib-nano-malloc --enable-newlib-nano-formatted-io --enable-newlib-reent-small --prefix=path_to/esp-open-rtos/libc

CROSS_CFLAGS="-DSIGNAL_PROVIDED -DABORT_PROVIDED" make
make install

Closes #95

libc/xtensa-lx106-elf/include/config.h

@@ -0,0 +1,43 @@
+#ifndef __SYS_CONFIG_H__
+#define __SYS_CONFIG_H__
+
+#include <machine/ieeefp.h>  /* floating point macros */
+#include <sys/features.h>	/* POSIX defs */
+
+/*************************************************************************
+ esp8266-specific xtensa stuff
+ *************************************************************************/
+
+#ifndef _REENT_SMALL
+#define _REENT_SMALL
+#endif
+
+/* esp8266 hardware FIFO buffers are 128 bytes */
+#define __BUFSIZ__ 128
+
+/*************************************************************************
+ end of esp8266-specific stuff
+ *************************************************************************/
+
+#ifndef __EXPORT
+#define __EXPORT
+#endif
+
+#ifndef __IMPORT
+#define __IMPORT
+#endif
+
+/* Define return type of read/write routines.  In POSIX, the return type
+   for read()/write() is "ssize_t" but legacy newlib code has been using
+   "int" for some time.  If not specified, "int" is defaulted.  */
+#ifndef _READ_WRITE_RETURN_TYPE
+#define _READ_WRITE_RETURN_TYPE int
+#endif
+/* Define `count' parameter of read/write routines.  In POSIX, the `count'
+   parameter is "size_t" but legacy newlib code has been using "int" for some
+   time.  If not specified, "int" is defaulted.  */
+#ifndef _READ_WRITE_BUFSIZE_TYPE
+#define _READ_WRITE_BUFSIZE_TYPE int
+#endif
+
+#endif /* __SYS_CONFIG_H__ */