Add a no-egd option to disable EGD-related code

The entropy-gathering daemon is used only on a small number of machines.
Provide a configure knob so that EGD support can be disabled by default
but re-enabled on those systems that do need it.

Reviewed-by: Dr. Stephen Henson <steve@openssl.org>

Configure

diff --git a/Configure b/Configure
index c309485..7126659 100755
--- a/Configure
+++ b/Configure
@@ -14,7 +14,7 @@
 
 # see INSTALL for instructions.
 
-my $usage="Usage: Configure [no-<cipher> ...] [enable-<cipher> ...] [experimental-<cipher> ...] [-Dxxx] [-lxxx] [-Lxxx] [-fxxx] [-Kxxx] [no-hw-xxx|no-hw] [[no-]threads] [[no-]shared] [[no-]zlib|zlib-dynamic] [no-asm] [no-dso] [sctp] [386] [--prefix=DIR] [--openssldir=OPENSSLDIR] [--with-xxx[=vvv]] [--test-sanity] [--config=FILE] os/compiler[:flags]\n";
+my $usage="Usage: Configure [no-<cipher> ...] [enable-<cipher> ...] [experimental-<cipher> ...] [-Dxxx] [-lxxx] [-Lxxx] [-fxxx] [-Kxxx] [no-hw-xxx|no-hw] [[no-]threads] [[no-]shared] [[no-]zlib|zlib-dynamic] [no-asm] [no-dso] [no-egd] [sctp] [386] [--prefix=DIR] [--openssldir=OPENSSLDIR] [--with-xxx[=vvv]] [--test-sanity] [--config=FILE] os/compiler[:flags]\n";
 
 # Options:
 #
@@ -50,6 +50,7 @@
 # no-asm        do not use assembler
 # no-dso        do not compile in any native shared-library methods. This
 #               will ensure that all methods just return NULL.
+# no-egd        do not compile support for the entropy-gathering daemon APIs
 # [no-]zlib     [don't] compile support for zlib compression.
 # zlib-dynamic	Like "zlib", but the zlib library is expected to be a shared
 #		library and will be loaded in run-time by the OpenSSL library.
@@ -905,6 +906,7 @@
 
 my %disabled = ( # "what"         => "comment" [or special keyword "experimental"]
 		 "ec_nistp_64_gcc_128" => "default",
+		 "egd"            => "default",
 		 "jpake"          => "experimental",
 		 "md2"            => "default",
 		 "rc5"            => "default",