The parameter `template` in format_call_external_argv() was renamed
to `template_fmt` to avoid collision with the `template` keyword in
C++. This improves compatibility when the header is included in
C++ code.
Some functions were declared without parameters in header files,
despite their implementations specifying arguments. This mismatch
is deprecated in all versions of C and is disallowed in C23.
This change updates the declarations to match their definitions,
ensuring compatibility with C standards, avoiding potential
undefined behavior, and improving support in tools and editors.
This change adds necessary `#include` directives that were previously
omitted in some header files. Without these includes, compilation
could fail or produce undefined behavior when the headers are used
in isolation (i.e., before their dependencies are included elsewhere).
Ensures better modularity and reliability of header usage.
