Fix clang warnings, add clang to travis

Jan Breuer

2015-10-04 df3eeb1a9be519b5eaef18b8f7c2d7a201bf7b97

 examples/common/scpi-def.h

@@ -9,7 +9,6 @@
int SCPI_Error(scpi_t * context, int_fast16_t err);
scpi_result_t SCPI_Control(scpi_t * context, scpi_ctrl_name_t ctrl, scpi_reg_val_t val);
scpi_result_t SCPI_Reset(scpi_t * context);
scpi_result_t SCPI_Test(scpi_t * context);
scpi_result_t SCPI_Flush(scpi_t * context);