refactor: rename PIP_NO_\* to PIP_HAS_\* with inverted logic

All feature flags now use positive naming (enabled by default):
- PIP_HAS_FILESYSTEM, PIP_HAS_THREADS, PIP_HAS_SOCKET
- PIP_HAS_PROCESS, PIP_HAS_DYNLIB, PIP_HAS_FFT, PIP_HAS_SERIAL

Preprocessor guards inverted:
- #ifndef PIP_NO_X → #ifdef PIP_HAS_X
- #ifdef PIP_NO_X → #ifndef PIP_HAS_X

CMake options default ON instead of OFF.
Platform blocks set flags OFF to disable features.

85 files transformed via Python script + 2 manual fixes.

libs/main/io_devices/pifile.h

@@ -31,7 +31,7 @@
 #include "pipropertystorage.h"
 
 
-#ifndef PIP_NO_FILESYSTEM
+#ifdef PIP_HAS_FILESYSTEM
 //! \~\ingroup IO
 //! \~\brief
 //! \~english Local file.
@@ -362,10 +362,10 @@ private:
 	llong _size = -1;
 	PIString prec_str;
 };
-#endif // PIP_NO_FILESYSTEM
+#endif // PIP_HAS_FILESYSTEM
 
 
-#ifndef PIP_NO_FILESYSTEM
+#ifdef PIP_HAS_FILESYSTEM
 //! \relatesalso PICout
 //! \~english Output operator to \a PICout.
 //! \~russian Оператор вывода в \a PICout.
@@ -398,6 +398,6 @@ BINARY_STREAM_READ(PIFile::FileInfo) {
 		v.perm_group.raw >> v.perm_other.raw;
 	return s;
 }
-#endif // PIP_NO_FILESYSTEM
+#endif // PIP_HAS_FILESYSTEM
 
 #endif // PIFILE_H