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/core/picout.cpp

@@ -709,7 +709,7 @@ void PICout::applyFormat(PICoutFormat f) {
 }
 
 
-#ifndef PIP_NO_THREADS
+#ifdef PIP_HAS_THREADS
 PIString PICout::getBuffer() {
 	PIMutexLocker ml(PICout::__mutex__());
 	PIString ret = PICout::__string__();
@@ -729,7 +729,7 @@ void PICout::clearBuffer() {
 	PIMutexLocker ml(PICout::__mutex__());
 	PICout::__string__().clear();
 }
-#endif // PIP_NO_THREADS
+#endif // PIP_HAS_THREADS
 
 
 bool PICout::setOutputDevice(PICout::OutputDevice d, bool on) {