PR modula2/115057 TextIO.ReadRestLine raises an exception when buffer is exceeded

PR modula2/115057 TextIO.ReadRestLine raises an exception when buffer is exceeded

TextIO.ReadRestLine will raise an "attempting to read beyond end of file"
exception if the buffer is exceeded.  This bug is caused by the
TextIO.ReadRestLine calling IOChan.Skip without a preceeding IOChan.Look.
The Look procedure will update the status result whereas
Skip always sets read result to allRight.

gcc/m2/ChangeLog:

	PR modula2/115057
	* gm2-libs-iso/TextIO.mod (ReadRestLine): Use ReadChar to
	skip unwanted characters as this calls IOChan.Look and updates
	the cid result status.  A Skip without a Look does not update
	the status.  Skip always sets read result to allRight.
	* gm2-libs-iso/TextUtil.def (SkipSpaces): Improve comments.
	(CharAvailable): Improve comments.
	* gm2-libs-iso/TextUtil.mod (SkipSpaces): Improve comments.
	(CharAvailable): Improve comments.

gcc/testsuite/ChangeLog:

	PR modula2/115057
	* gm2/isolib/run/pass/testrestline.mod: New test.
	* gm2/isolib/run/pass/testrestline2.mod: New test.
	* gm2/isolib/run/pass/testrestline3.mod: New test.

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