Compiler warning cleanup
Fix up compiler warnings from gcc 14 & clang 13:
- Clear 9
-Wuseless-cast
warnings - Fix
-Wshadow
warning forDisplay
argument toError()
- Fix
-Wself-assign
warning from clang 13 - Fix
-Wmissing-variable-declarations
warning from clang 13 - usage: add
noreturn
attribute - Quiet 64
-Wunused-parameter
warnings from clang 13 - Use double for all floating point numbers, not a mix of double and float