[PATCH] Cleanup: require config.h or squid.h first in .c and .cc files

These are the code fixes identified by the altered enforcement script
which checks the first #include file of each .c/.cc. (separate patch
submission)

  * config.h has been used where none was present so as not to introduce
new dependencies

  * some order shuffling for squid.h included too late found and fixed

If there are no objections I'll commit after confirming there are no
build problems on FreeBSB, Debian, Ubuntu. If anyone can do a build
check on other systems and provide feedback that would be great.

Amos