Move to PROGMEM aware libc, allow PSTR in printf()

A Newlib (libc) patch is in progress to move the _P functions from inside
Arduino into first-class citizens in libc.  This Arduino patch cleans up
code that's been migrated there.  Binaries for the new libs are included
because it seems they're part of the Arduino git tree, and should be
replaced with @igrr built ones when/if the Newlib changes are accepted.

Notable changes/additions for Arduino:
Allow for use of PROGMEM based format and parameter strings in all
*printf functions.  No need for copying PSTR()s into RAM before printing
them out (transparently saves heap space when using _P functions) and
makes it easier to print out constant strings for applications.

Add "%S" (capital-S) format that I've been told, but cannot verify,
is used in Arduino to specify a PROGMEM string parameter in printfs,
as an alias for "%s" since plain "%s" can now handle PROGMEM.

Optimized the memcpy_P, strnlen_P, and strncpy_P functions to use 32-bit
direct reads whenver possible (source and dest alignment mediated), but
there is still room for improvement in others.

Finally, move several constant arrays from RODATA into PROGMEM and
update their accessors.  Among these are the ctype array, ~260 bytes,
mprec* arrays, ~300 bytes, and strings/daycounts in the time
formatting functions, ~200 bytes.  All told, sketches will see from
300 to 800 additional RAM heap free on startup (depending on their
use of these routines).

Author: earlephilhower

cores/esp8266/libc_replacements.c

@@ -121,40 +121,3 @@ void _exit(int status) {
     (void) status;
     abort();
 }
-
-#if 0
-
-int ICACHE_RAM_ATTR printf(const char* format, ...) {
-    va_list arglist;
-    va_start(arglist, format);
-    int ret = ets_vprintf(ets_putc, format, arglist);
-    va_end(arglist);
-    return ret;
-}
-
-int ICACHE_RAM_ATTR sprintf(char* buffer, const char* format, ...) {
-    int ret;
-    va_list arglist;
-    va_start(arglist, format);
-    ret = ets_vsprintf(buffer, format, arglist);
-    va_end(arglist);
-    return ret;
-}
-
-int ICACHE_RAM_ATTR snprintf(char* buffer, size_t size, const char* format, ...) {
-    int ret;
-    va_list arglist;
-    va_start(arglist, format);
-    ret = ets_vsnprintf(buffer, size, format, arglist);
-    va_end(arglist);
-    return ret;
-}
-
-int ICACHE_RAM_ATTR vprintf(const char * format, va_list arg) {
-    return ets_vprintf(ets_putc, format, arg);
-}
-
-int ICACHE_RAM_ATTR vsnprintf(char * buffer, size_t size, const char * format, va_list arg) {
-    return ets_vsnprintf(buffer, size, format, arg);
-}
-#endif