Revert macros in espressif#7941, but simplify.

Author: dok-net

Diff for: cores/esp32/WString.h

@@ -34,8 +34,8 @@
 // A pure abstract class forward used as a means to proide a unique pointer type
 // but really is never defined.
 class __FlashStringHelper;
-#define FPSTR(pstr_pointer) (pstr_pointer)
-#define F(string_literal) (string_literal)
+#define FPSTR(str_pointer) (reinterpret_cast<const __FlashStringHelper *>(str_pointer))
+#define F(string_literal) (FPSTR(string_literal))
 
 // An inherited class for holding the result of a concatenation.  These
 // result objects are assumed to be writable by subsequent concatenations.