Makefile: update the default build options for AIX

NO_MKDTEMP is required to build, FREAD_READS_DIRECTORIES and the definition
of _LARGE_FILES fix test suite failures and INTERNAL_QSORT is required for
adequate performance.

Tested on AIX v5.3 Maintenance Level 06
Signed-off-by: NMike Ralphson <mike@abacus.co.uk>
Tested-by: NJohannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Makefile

@@ -636,8 +636,12 @@ endif
 ifeq ($(uname_S),AIX)
 	NO_STRCASESTR=YesPlease
 	NO_MEMMEM = YesPlease
+	NO_MKDTEMP = YesPlease
 	NO_STRLCPY = YesPlease
+	FREAD_READS_DIRECTORIES = UnfortunatelyYes
+	INTERNAL_QSORT = UnfortunatelyYes
 	NEEDS_LIBICONV=YesPlease
+	BASIC_CFLAGS += -D_LARGE_FILES
 endif
 ifeq ($(uname_S),GNU)
 	# GNU/Hurd