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/Makefile.am

@@ -28,7 +28,7 @@ EXTRA_DIST = ftpserver.pl httpserver.pl secureserver.pl runtests.pl getpart.pm \
  sshserver.pl sshhelp.pm testcurl.1 runtests.1 $(HTMLPAGES) $(PDFPAGES) \
  CMakeLists.txt certs/scripts/*.sh certs/Server* certs/EdelCurlRoot* \
  serverhelp.pm tftpserver.pl rtspserver.pl directories.pm symbol-scan.pl \
- certs/srp-verifier-conf certs/srp-verifier-db
+ certs/srp-verifier-conf certs/srp-verifier-db mem-include-scan.pl
 
 # we have two variables here to make sure DIST_SUBDIRS won't get 'unit'
 # added twice as then targets such as 'distclean' misbehave and try to