provide the spacing commands for math also in text (as amsmath does)

[FrankMittelbach]

Brief outline of the enhancement

Core LaTeX only offers \, in math and text while \:, \; and \! are only available in math. However, all of them are quite useful for text but there only \negthinspace (long form of \! is available.

In contrast amsmath once loaded makes all of them available in text and math. This should be moved to the kernel to be always available.

Minimal example showing the current behaviour

\RequirePackage{latexbug}       % <--should be always the first line (see CONTRIBUTING)!
\documentclass{article}

%\usepackage{amsmath}
\setlength{\parindent}{0pt}

\begin{document}

X\,X \par
X\:X \par
X\;X \par
X\!X \par

\end{document}

Minimal example showing the desired new behaviour

no error in the above document when amsmath is not loaded