PR modula2/114836 Avoid concatenation of error strings to aid error locale translation

This patch avoids a concatenation of error strings making locale
translation of the error message easier.

gcc/m2/ChangeLog:

	PR modula2/114836
	* gm2-compiler/M2Range.mod (FoldTypeAssign): Avoid error
	string concatenation.

Signed-off-by: Gaius Mulley <gaiusmod2@gmail.com>