Support #pragma in struct declarations

[ldore]

Pragmas do not seem to be supported within typedefs.
Updating tests.test_c_generator.TestCtoC.test_pragma to:

    def test_pragma(self):
        self._assert_ctoc_correct(r'''
            #pragma foo
            void f() {
                #pragma bar
                i = (a, b, c);
            }
            typedef struct s {
            #pragma baz
            } s;
        ''')

raises a ParseError.

This occured in a source similar to:

typedef struct MyStruct {
    int a;
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
    int b;
#pragma GCC diagnostic pop
}

[myint]

Perhaps this should be closed (#222)?