versioner: fix off-by-one error in header guard calculation.

This was causing redundant guards to be emitted in cases where
declarations were already guarded by another macro.

Bug: http://b/30170081
Change-Id: I9080838fbea5a56225df4b26d0918657fb6c4f21
Test: python run_tests.py
diff --git a/tools/versioner/tests/preprocessor/headers/foo.h b/tools/versioner/tests/preprocessor/headers/foo.h
index ae5b847..7eba47f 100644
--- a/tools/versioner/tests/preprocessor/headers/foo.h
+++ b/tools/versioner/tests/preprocessor/headers/foo.h
@@ -2,25 +2,41 @@
 
 int also_always_available() __INTRODUCED_IN(9);
 
-int needs_guard() __INTRODUCED_IN(10);
+int needs_guard() __INTRODUCED_IN(13);
 
-#if __ANDROID_API__ >= 10
-int already_guarded() __INTRODUCED_IN(10);
+#if __ANDROID_API__ >= 12
+int needs_guard_2() __INTRODUCED_IN(13);
+#endif
+
+#if __ANDROID_API__ >= 13
+int already_guarded() __INTRODUCED_IN(13);
+#endif
+
+#if __ANDROID_API__ > 13
+int already_guarded_2() __INTRODUCED_IN(13);
 #endif
 
 #if defined(__arm__)
-int specific_arch() __INTRODUCED_IN(11);
+int specific_arch() __INTRODUCED_IN(14);
+
+#if __ANDROID_API__ >= 14
+int specific_arch_already_guarded() __INTRODUCED_IN(14);
+#endif
+
+#if __ANDROID_API__ > 14
+int specific_arch_already_guarded_2() __INTRODUCED_IN(14);
+#endif
 #endif
 
 #if defined(__arm__) || defined(__i386__)
-int multiple_archs() __INTRODUCED_IN(11);
+int multiple_archs() __INTRODUCED_IN(14);
 #endif
 
 // __INTRODUCED_IN_64(21) should be ignored.
-int multiple_introduced_1() __INTRODUCED_IN_ARM(10) __INTRODUCED_IN_MIPS(11) __INTRODUCED_IN_X86(10)
+int multiple_introduced_1() __INTRODUCED_IN_ARM(13) __INTRODUCED_IN_MIPS(14) __INTRODUCED_IN_X86(13)
     __INTRODUCED_IN_64(21);
 
-int multiple_introduced_2() __INTRODUCED_IN_ARM(10) __INTRODUCED_IN_MIPS(11) __INTRODUCED_IN_X86(10)
+int multiple_introduced_2() __INTRODUCED_IN_ARM(13) __INTRODUCED_IN_MIPS(14) __INTRODUCED_IN_X86(13)
     __INTRODUCED_IN_64(22);
 
 int group_lp32() __INTRODUCED_IN_ARM(12) __INTRODUCED_IN_X86(12) __INTRODUCED_IN_MIPS(12);