patch: busyboxify by migrating from toybox to busybox helpers

function                                             old     new   delta
get_line                                              90     128     +38
bbconfig_config_bz2                                 4959    4965      +6
makedevs_main                                       1038    1035      -3
fail_hunk                                            133     130      -3
finish_oldfile                                       174     124     -50
patch_main                                          2066    1987     -79
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/4 up/down: 44/-135)           Total: -91 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/testsuite/patch.tests b/testsuite/patch.tests
index e482304..ba37e82 100755
--- a/testsuite/patch.tests
+++ b/testsuite/patch.tests
@@ -75,7 +75,7 @@
 testing "patch detects already applied hunk" \
 	'patch 2>&1; echo $?; cat input' \
 "\
-Possibly reversed hunk 1 at 2
+Possibly reversed hunk 1 at 4
 Hunk 1 FAILED 1/1.
  abc
 +def
@@ -103,7 +103,7 @@
 testing "patch detects already applied hunk at the EOF" \
 	'patch 2>&1; echo $?; cat input' \
 "\
-Possibly reversed hunk 1 at 3
+Possibly reversed hunk 1 at 4
 Hunk 1 FAILED 1/1.
  abc
  123