c-mode: respect user defined tab width in indentation

Example:
1. set a custom tab width via `set-tab-width` (e.g., 4).
2. open c-mode, type of block of C code, and indent.

Expected behavior: One tab character per indentation level (or spaces if no-tab-mode enabled).
Actual behavior: Multiple tabs/spaces inserted to reach an indentation of 8 columns.

This patch updates `getindent` to respect the user-defined tab width
(`curbp->b_tabw`) when calculating indentation levels, instead of
always assuming 8 columns.

Previously, when the user set `set-tab-width` to 4, `c-mode` would
request 8 columns of indentation, resulting in two tab characters
being inserted instead of one. This caused incorrect indentation
for KNF-compliant code.

src/cmode.c

@@ -22,9 +22,6 @@
 extern int changemode(int, int, char *);
 
 static int cc_strip_trailp = TRUE;	/* Delete Trailing space? */
-static int cc_basic_indent = 8;		/* Basic Indent multiple */
-static int cc_cont_indent = 4;		/* Continued line indent */
-static int cc_colon_indent = -8;	/* Label / case indent */
 
 static int getmatch(int, int);
 static int getindent(const struct line *, int *);
@@ -324,17 +321,17 @@ getindent(const struct line *lp, int *curi)
 	 * we continue
 	 */
 	if (colonp) {
-		*curi += cc_colon_indent;
-		newind -= cc_colon_indent;
+		*curi += -curbp->b_tabw;
+		newind -= -curbp->b_tabw;
 	}
 
-	*curi -= (cbrace) * cc_basic_indent;
-	newind += obrace * cc_basic_indent;
+	*curi -= (cbrace) * curbp->b_tabw;
+	newind += obrace * curbp->b_tabw;
 
 	if (nparen < 0)
-		newind -= cc_cont_indent;
+		newind -= curbp->b_tabw / 2;
 	else if (nparen > 0)
-		newind += cc_cont_indent;
+		newind += curbp->b_tabw / 2;
 
 	*curi += nicol;