Fix compile warnings for target=armv7-android-gcc

Fix compile warnings about implicit type conversion for
target=armv7-android-gcc in aomenc.c.

cherry-picked from libvpx:
380a26112 Fix compile warnings for target=armv7-android-gcc

BUG=aomedia:111

Change-Id: Iffa6af8ac5d87582f418e3425bee0e1d48f27b93
diff --git a/tools_common.h b/tools_common.h
index 6d3688a..0375003 100644
--- a/tools_common.h
+++ b/tools_common.h
@@ -27,11 +27,23 @@
 /* MSVS uses _f{seek,tell}i64. */
 #define fseeko _fseeki64
 #define ftello _ftelli64
+typedef int64_t FileOffset;
 #elif defined(_WIN32)
+#include <sys/types.h> /* NOLINT*/
 /* MinGW uses f{seek,tell}o64 for large files. */
 #define fseeko fseeko64
 #define ftello ftello64
-#endif /* _WIN32 */
+typedef off64_t FileOffset;
+#elif CONFIG_OS_SUPPORT
+#include <sys/types.h> /* NOLINT*/
+typedef off_t FileOffset;
+/* Use 32-bit file operations in WebM file format when building ARM
+ * executables (.axf) with RVCT. */
+#else
+#define fseeko fseek
+#define ftello ftell
+typedef long FileOffset /* NOLINT */
+#endif /* CONFIG_OS_SUPPORT */
 
 #if CONFIG_OS_SUPPORT
 #if defined(_MSC_VER)
@@ -43,13 +55,6 @@
 #endif              /* _MSC_VER */
 #endif              /* CONFIG_OS_SUPPORT */
 
-/* Use 32-bit file operations in WebM file format when building ARM
- * executables (.axf) with RVCT. */
-#if !CONFIG_OS_SUPPORT
-#define fseeko fseek
-#define ftello ftell
-#endif /* CONFIG_OS_SUPPORT */
-
 #define LITERALU64(hi, lo) ((((uint64_t)hi) << 32) | lo)
 
 #ifndef PATH_MAX