mem-include-scan: verify memory #includes

If we use memory functions (malloc, free, strdup etc) in C sources in
libcurl and we fail to include curl_memory.h or memdebug.h we either
fail to properly support user-provided memory callbacks or the memory
leak system of the test suite fails.

After Ajit's report of a failure in the first category in http_proxy.c,
I spotted a few in the second category as well. These problems are now
tested for by test 1132 which runs a perl program that scans for and
attempts to check that we use the correct include files if a memory
related function is used in the source code.

Reported by: Ajit Dhumale
Bug: http://curl.haxx.se/mail/lib-2012-11/0125.html

tests/data/test1132

@@ -0,0 +1,24 @@
+<testcase>
+<info>
+<keywords>
+memory-includes
+</keywords>
+</info>
+
+#
+# Client-side
+<client>
+<server>
+none
+</server>
+
+ <name>
+Verify memory #include files in libcurl's C source files
+ </name>
+
+<command type="perl">
+%SRCDIR/mem-include-scan.pl %SRCDIR/../lib
+</command>
+</client>
+
+</testcase>