Added 'Requires:' line to libssh2.pc.

This is necessary so that other libs which lookup libssh2 info
via pkg-config can add the right crypto lib dependencies.

configure.ac

@@ -96,13 +96,17 @@ AC_ARG_WITH(libz,
 # Look for OpenSSL (default)
 if test "$use_openssl" != "no" && test "$use_libgcrypt" != "yes"; then
   AC_LIB_HAVE_LINKFLAGS([ssl], [crypto], [#include <openssl/ssl.h>])
+  LIBSREQUIRED=ssl,crypto
 fi
 
 # Look for libgcrypt
 if test "$ac_cv_libssl" != "yes" && test "$use_libgcrypt" != "no"; then
   AC_LIB_HAVE_LINKFLAGS([gcrypt], [], [#include <gcrypt.h>])
+  LIBSREQUIRED=gcrypt
 fi
 
+AC_SUBST(LIBSREQUIRED)
+
 if test "$ac_cv_libssl" != "yes" && test "$ac_cv_libgcrypt" != "yes"; then
   AC_MSG_ERROR([cannot find OpenSSL or Libgcrypt,
 try --with-libssl-prefix=PATH or --with-libgcrypt-prefix=PATH])

libssh2.pc.in

@@ -11,6 +11,7 @@ Name: libssh2
 URL: http://www.libssh2.org/
 Description: Library for SSH-based communication
 Version: @LIBSSH2VER@
+Requires: @LIBSREQUIRED@
 Libs: -L${libdir} -lssh2 @LDFLAGS@ @LIBS@
 Libs.private: @LIBS@
 Cflags: -I${includedir}