Moved api examples to "ext" dir and hooked them into autotools for building with "--enable-extentions".

Upgraded to autoconf 2.65.

ext/README

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+Custom ModSecurity Modules
+--------------------------
+
+This directory contains three examples how you can extend
+ModSecurity without having to touch it directly, simply
+by creating custom Apache modules.
+
+NOTE: ModSecurity must be compiled with API support
+      to use this feature (the API is enabled by default,
+      but it will have been disabled if you used -DNO_MODSEC_API).
+
+
+Building the Example Custom Modules
+-----------------------------------
+
+1) Example custom transformation function module
+
+Module mod_tfn_reverse.c creates a custom transformation
+function "reverse" that reverses the content it receives
+on input.
+
+# Compile as a normal user
+  apxs -I<MODSECURITY_SOURCE_CODE> -I/usr/include/libxml2 \
+       -ca mod_tfn_reverse.c
+
+  # Install as superuser
+  sudo apxs -i mod_tfn_reverse.la
+
+
+2) Example custom operator module
+
+Module mod_op_strstr.c creates a custom operator "strstr"
+that implements fast matching using the Boyer-Moore-Horspool
+algorithm.
+
+  # Compile as a normal user
+  apxs -I<MODSECURITY_SOURCE_CODE> -I/usr/include/libxml2 \
+       -ca mod_op_strstr.c
+
+  # Install as superuser
+  sudo apxs -i mod_op_strstr.la
+
+
+3) Example custom target variable module
+
+Module mod_var_remote_addr_port.c creates a custom variable "REMOTE_ADDR_PORT"
+that combines the REMOTE_ADDR and REMOTE_PORT into a.b.c.d:port format.
+
+  # Compile as a normal user
+  apxs -I<MODSECURITY_SOURCE_CODE> -I/usr/include/libxml2 \
+       -ca mod_var_remote_addr_port.c
+
+  # Install as superuser
+  sudo apxs -i mod_var_remote_addr_port.la
+
+
+Using the Modules
+-----------------
+
+Once the modules are built and installed, you load them like any other Apache module, but they must be loaded *after* the mod_security2.so module.
+
+  # Load ModSecurity
+  LoadModule security2_module modules/mod_security2.so
+
+  # Load ModSecurity custom modules
+  LoadModule tfn_reverse_module modules/mod_tfn_reverse.so
+  LoadModule op_strstr_module modules/mod_op_strstr.so
+  LoadModule var_remote_addr_port_module modules/mod_var_remote_addr_port.so
+
+  # All three custom var/op/tfn used
+  SecRule REMOTE_ADDR_PORT "@strstr 1.2.3.4:5678" "t:reverse"
+