Preprocessor cannot correctly parse TFs without any whitespaces

Make the preprocessor accept strings like "thetas1+thetas2CLYPPT_M+thetas3BLDFIE_M+thetas4SLTPPT_M**(2.0)+thetas5ORCDRC_M**(2.0)+thetas6CLYPPT_M**(-1.0)+thetas7SLTPPT_M**(-1.0)+thetas8log(SLTPPT_M)+thetas9ORCDRC_MCLYPPT_M-thetas10BLDFIE_MCLYPPT_M-thetas11BLDFIE_MORCDRC_M+thetas12topsoil*SLTPPT_M" and correctly insert line break in produced source code.