Improve error handling and other C89 improvements #31

Job	Run time
Test Amalgamation	11s
build / Win Cygwin \| Static Lib \| Unicode \| Single-thread \| LTO OFF \| FetchContent	3m 42s
build / Win MinGW \| Static Lib \| Unicode \| Single-thread \| LTO ON \| FetchContent	1m 25s
build / Win MSVC Latest \| Shared Lib (MD) \| Unicode \| LTO OFF \| Multi-thread \| FetchContent	44s
build / Win MSVC Latest \| Static Lib (MDd) \| Unicode \| LTO OFF \| Multi-thread \| System \| RTCu	49s
build / Win MSVC Latest \| Static Lib (MT) \| ANSI \| LTO ON \| Single-thread \| Vcpkg \| RTC1	41s
build / Win MSVC 2022 \| Shared Lib (MTd) \| ANSI \| LTO OFF \| Single-thread \| FetchContent \| RTCs	38s
build / Linux GCC \| Shared Lib \| Unicode \| Multi-thread \| LTO OFF \| Vcpkg	31s
build / Win MinGW \| Shared Lib \| ANSI \| Multi-thread \| LTO OFF \| System	1m 23s
build / Linux GCC \| Static Lib \| ANSI \| Single-thread \| LTO ON \| FetchContent	22s
build / macOS Clang \| Static Lib \| ANSI \| Single-thread \| LTO OFF \| System	24s
build / macOS Clang \| Shared Lib \| Unicode \| Multi-thread \| LTO ON \| FetchContent	17s
build / Linux Clang \| Shared Lib \| Unicode \| Multi-thread \| LTO OFF \| Vcpkg	24s
build / Linux Clang \| Static Lib \| ANSI \| Single-thread \| LTO ON \| System	24s
	11m 55s

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