Add native vector_lenght() function which calculates the euclidean distance 80%

faster. See https://github.com/matiasdelellis/pdlib/pull/2.

Increase the version to 1.0.2 since this is a required function for our
application and we must control it.

Add more compilation info in php-info(), and print a final message with the
build options when configure.

Fix that when dlib is not installed, the configuration returns that it cannot
find pkgconfig. See https://github.com/matiasdelellis/facerecognition/issues/261

Also implement the test on travis. See for example:
(https://travis-ci.com/github/matiasdelellis/pdlib/builds/161854044)

config.m4

@@ -1,10 +1,3 @@
-dnl $Id$
-dnl config.m4 for extension pdlib
-
-dnl Comments in this file start with the string 'dnl'.
-dnl Remove where necessary. This file will not work
-dnl without editing.
-
 if test -z "$PHP_DEBUG"; then
     AC_ARG_ENABLE(debug,
     [   --enable-debug          compile with debugging symbols],[
@@ -27,26 +20,49 @@ if test "$PHP_PDLIB" != "no"; then
   src/face_detection.cc \
   src/face_landmark_detection.cc \
   src/face_recognition.cc \
-  src/cnn_face_detection.cc "
+  src/cnn_face_detection.cc
+  src/vector.cc"
 
   AC_MSG_CHECKING(for pkg-config)
   AC_PATH_PROG(PKG_CONFIG, pkg-config, no)
-
-  if test -x "$PKG_CONFIG" && $PKG_CONFIG --exists dlib-1; then
-     if $PKG_CONFIG dlib-1 --atleast-version 19.00; then
+  if test -x "$PKG_CONFIG"; then
+    AC_MSG_RESULT(found)
+    AC_MSG_CHECKING(for dlib-1)
+    if $PKG_CONFIG --exists dlib-1; then
+      if $PKG_CONFIG dlib-1 --atleast-version 19.00; then
         LIBDLIB_CFLAGS=`$PKG_CONFIG dlib-1 --cflags`
         LIBDLIB_LIBDIR=`$PKG_CONFIG dlib-1 --libs`
         LIBDLIB_VERSON=`$PKG_CONFIG dlib-1 --modversion`
         AC_MSG_RESULT(from pkgconfig: dlib version $LIBDLIB_VERSON)
-     else
+      else
         AC_MSG_ERROR(system dlib is too old: version 19.00 required)
-     fi
+      fi
+    else
+      AC_MSG_ERROR(dlib-1 not found)
+    fi
   else
      AC_MSG_ERROR(pkg-config not found)
   fi
+
   PHP_EVAL_LIBLINE($LIBDLIB_LIBDIR, PDLIB_SHARED_LIBADD)
   PHP_EVAL_INCLINE($LIBDLIB_CFLAGS)
 
   dnl using C++11
   PHP_NEW_EXTENSION(pdlib, $pdlib_src_files, $ext_shared,, -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1 -std=c++11, cxx)
 fi
+
+AC_CONFIG_COMMANDS_POST([
+  echo ""
+  echo "Build configuration for PDlib v1.0.2 done correctly."
+  echo ""
+  echo "  dlib version: $LIBDLIB_VERSON"
+  echo ""
+  echo "  CXXFLAGS    : $CXXFLAGS"
+  echo "  LDFLAGS     : $LDFLAGS"
+  echo "  LIBDIR:     : $LIBDLIB_LIBDIR"
+  echo "  LIBADD:     : $PDLIB_SHARED_LIBADD"
+  echo ""
+  echo "Please submit bug reports at:"
+  echo "  https://github.com/goodspb/pdlib/issues"
+  echo ""
+])