Removes pre-C99 build and header cruft (#700)

* Committing clang-format changes

* Removes pre-C99 build and header cruft

* Assumes ANSI C headers exist
* Assumes stdbool.h, stdint.h, and inttypes.h are present
* Assumes the C++ compiler can handle stdint.h
* Removes all work-arounds for missing functionality, especially stdbool.h

* Formats source

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

config/cmake_ext_mod/HDFTests.c

@@ -88,14 +88,6 @@ int main(void)
 }
 #endif
 
-#ifdef STDC_HEADERS
-#include <stdlib.h>
-#include <stdarg.h>
-#include <string.h>
-#include <float.h>
-int main() { return 0; }
-#endif /* STDC_HEADERS */
-
 
 #ifdef HAVE_ATTRIBUTE