bladeRF-cli: Added -e <command> support

This option allows interactive mode commands to be executed from the
command line. Multiple -e <cmd> arguments may be provided; they will be
executed in the order they are specified.

Operations/command are performed in the following order:
    - Command line options (e.g., FPGA load, firmware flash)
    - Commands from '-e <cmd>' arguments
    - Commands from script files
    - Interactive mode commands
bladeRF-cli: Differentiate between file "not found" and I/O errors
bladeRF-cli: Cleaned up items reported by Clang static analysis

tx.c - Removed dead assignment, fixed leak due to incorrect status check
main.c - Memory leaks in rc_config items
conversions.c - Removed dead assignment
script.c - fileno() doesn't fail when given valid FILE*. Removed false positive.
libbladeRF: Addressed items identified by Clang scan

tests/test_sync/src/test.c:
    Changed sample buffer type to int16_t. These alleivates noise from static
    analysis tools regarding a type mismatch with sizeof(), and better
    exemplifies the buffers that should be used in conjunction with the SC16 Q11
    format.

tests/test_repeater/src/repeater.c:
    Fixed unchecked pthread_cond_wait result.

tests/test_async/main.c:
    Fixed unchecked return values, minor cleanup.

src/lms.c:
    Removed dead assignment.

src/backend/usb/usb.c:
    Corrected unchecked return value.

src/backuend/usb/libusb.c:
    Fixed uninitialized variable in error path.