parser: remove strconv import

vlib/v/parser/parser.v

@@ -13,7 +13,6 @@ import v.errors
 import os
 import runtime
 import time
-import strconv
 
 pub struct Parser {
 	file_name         string // "/home/user/hello.v"
@@ -1203,12 +1202,12 @@ fn (mut p Parser) string_expr() ast.Expr {
 				if fields[0].len > 0 && fields[0][0] == `0` {
 					fill = true
 				}
-				fwidth = strconv.atoi(fields[0])
+				fwidth = fields[0].int()
 				if fwidthneg {
 					fwidth = -fwidth
 				}
 				if fields.len > 1 {
-					precision = strconv.atoi(fields[1])
+					precision = fields[1].int()
 				}
 				p.next()
 			}