Rename cabs/cimag/creal to mono_cabs/mono_cimag/mono_creal without macro to rename...

Rename cabs/cimag/creal to mono_cabs/mono_cimag/mono_creal without macro to rename. (mono/mono#13663)

Also make cimag/creal macros for guaranteed inlining -- instead of passing structs by value.
And add spaces before parens to follow coding convention (which is designed
to ease low tech searches for entire words).

This was agreed to when the code was first ported to C++ but got dropped.
The compromise though was to put the defines relatively late to limit their impact.

Commit migrated from https://github.com/mono/mono/commit/5ed727ed8ec595ad440c9f70a69d9bc970eccb86