Fix compilation on VS2013, Cygwin and MinGW.

- Link librtlsdr dynamically also on Windows.
rtl_test: Support PPM error measurement on Windows.
rtl_fm: Support output padding on Windows.
convenience: Don't show garbage when device information wasn't properly
extracted.
Add EditorConfig support
rtl_test: Don't use double when not needed.
Remove unused variables.
tuner_r82xx: Don't initialize variables when not needed.
Use proper type specifier.
Avoid possible null pointer dereference.
Explicitly cast to correct type to suppress MSVC warnings.