Headerfile.parse removes strips " from strings

If Headerfile.parse gets a headerfile string that already contains the parenthesis, for example in pystencils cuda kernels (check the test_cuda.py from the integration tests) it preseverse these and the emitted contains include directives with double parentheses. (Leading to a #include ""gpu_defines.hpp"") This MR fixes this and removes the " if they are already in the string