Auto-generate configuration flags.

This modifies import_openssl.sh to parse the configured Makefile
and extract the appropriate compiler flags that were currently
defined manually in android-config.mk

- Modifies openssl.config to add missing configure options to
  ensure the final result is the same than before the patch.
  This also updates crypto/opensslconf.h.

- The generated output is stored in build-config.mk which content
  directly comes from the OpenSSL Makefile.

- android-config.mk is still used to define LOCAL_CFLAGS from
  the definitions in build-config.mk, as well as perform minimal
  extra filtering.

- Remove the section in README.android about manually changing
  android-config.mk.

Change-Id: I5275de69a817aa7c9880ea48e5d6a8ac1652a1e4
diff --git a/README.android b/README.android
index 3583301..62456bf 100644
--- a/README.android
+++ b/README.android
@@ -75,17 +75,7 @@
 
      m -j16
 
-Optionally, check whether build flags (located in android-config.mk
-need to be updated.  Doing this step will help ensure that the
-compiled library is appropriately optimized for speed and size.  To
-update build flags:
-
-a) source openssl.config
-b) tar -zxf openssl-*.tar.gz
-c) cd openssl-*/
-d) ./Configure $CONFIGURE_ARGS
-e) examine Makefile and compare with ../android-config.mk
-f) modify ../openssl.config as appropriate and go to step 3) above.
-
-Alternatively, ."/import_openssl.sh import" now prints the
-post-Configure Makefile for review before deleting in on import.
+Optionally, check whether build flags (located in CONFIGURE_ARGS in
+openssl.config, plus some extras in android-config.mk), need to be updated.
+Doing this step will help ensure that the compiled library is appropriately
+optimized for speed and size.