clang-cl warnings

[gvanem]

While using clang-cl to build Jaero on Windows, I noticed these important warnings:

JAERO/burstmskdemodulator.cpp(724,22): warning: use of unary operator that may be intended as compound assignment (-=)
                real =- real;
                     ^~

Wasn't a real -= real; intended? But that seems a bit strange (resulting in almost zero?).

The same warning in several places:

JAERO/DSP.cpp(549,16): warning: use of unary operator that may be intended as compound assignment (-=)
        retval =- lastsoftstate;
               ^~

JAERO/mskdemodulator.cpp(461,18): warning: use of unary operator that may be intended as compound assignment (-=)
            real =- real;
                 ^~

JAERO/oqpskdemodulator.cpp(246,30): warning: use of unary operator that may be intended as compound assignment (-=)
        st_iir_resonator.b[2]=- 0.0012845857864470789;
                             ^~

Not sure about that last warning. But the first should be fixed by retval -= lastsoftstate;.