ts: add tests to improve --width option coverage

Author: xdelaruelle

testsuite/modules.70-maint/350-term_width.exp

@@ -286,6 +286,7 @@ unsetenv_var MODULES_TERM_WIDTH
 
 unsetenv_var MODULES_TERM_WIDTH
 testerr_cmd sh {avail loc_rc --width=0} $width_0
+testerr_cmd sh {avail loc_rc --width} $width_0
 testerr_cmd sh {avail loc_rc -w 0} $width_0
 testerr_cmd sh {avail loc_rc --width=1} $width_1
 testerr_cmd sh {avail loc_rc -w 1} $width_1
@@ -426,6 +427,7 @@ unsetenv_var MODULES_TERM_WIDTH
 
 unsetenv_var MODULES_TERM_WIDTH
 testerr_cmd sh {list --width=0} $width_0
+testerr_cmd sh {list --width=} $width_0
 testerr_cmd sh {list -w 1} $width_1
 testerr_cmd sh {list --width=80} $width_80