Only build the body of e_padlock when there are lower level routines

engines/e_padlock.c assumes that for all x86 and x86_64 platforms, the
lower level routines will be present.  However, that's not always
true, for example for solaris-x86-cc, and that leads to build errors.

The better solution is to have configure detect if the lower level
padlock routines are being built, and define the macro PADLOCK_ASM if
they are, and use that macro in our C code.

Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1510)
(cherry picked from commit 7b176a54)