Add SIP_THROW annotation

SIP uses the deprecated throw(...) annotation in order to determine
which exceptions may be thrown by c++ code. Without these, only
a generic unknown exception is throw, which is of limited value
to Python code (losing any valuable message and exception type).

So we add a new SIP_THROW macro, which can be added to method's
declaration:

    bool doSomething() SIP_THROW( QgsCsException );

This is ignored outside of sipify, so we don't actually use
the deprecated c++ throw annotations, but sipify picks it up
and adds the appropriate change to the sip definition for
the method:

   bool doSomething() throw( QgsCsException );

This means that calling the method from Python will raise
the QgsCsException instead of a generic exception.

scripts/sipify.pl

@@ -344,6 +344,7 @@ sub fix_annotations {
 
     $line =~ s/SIP_PYNAME\(\s*(\w+)\s*\)/\/PyName=$1\//;
     $line =~ s/SIP_VIRTUALERRORHANDLER\(\s*(\w+)\s*\)/\/VirtualErrorHandler=$1\//;
+    $line =~ s/SIP_THROW\(\s*(\w+)\s*\)/throw\( $1 \)/;
 
     # combine multiple annotations
     # https://regex101.com/r/uvCt4M/4

src/core/qgis_sip.h

@@ -169,6 +169,13 @@
  */
 #define SIP_VIRTUALERRORHANDLER(name)
 
+/*
+ * Throw - adds deprecated c++ throw calls for sip. Required for sip to add appropriate
+ * try/catch blocks around call and catch the correct exception, otherwise only
+ * unknown generic exceptions are available for Python code.
+ */
+#define SIP_THROW(name)
+
 /*
  * Will insert a `%End` directive in sip files
  */