* fix false positive warnings
* ONLY_FOR_PLATFORM => NOT_FOR_PLATFORM
* -Wl,-rpath
* include "../../mk/bsd.prefs.mk" before using "+=".
* include "../../mk/bsd.prefs.mk" before any .if
* warn about the use of ${SED} in {pre,do,post}-install
* check for direct use of user names and group names
* Find a reliable, secure way to delete all CVS directories inside
  ${WRKSRC}. When that is finished, add a warning that using ${XARGS}
  is insecure.
* detect spelling errors (like CONFLICT => CONFLICTS)
* warn about the use of ${WRKDIR:=...}, as this construct should only
  be used with lists.
* mention the SUBST framework whenever ${SED} is used.
* check that Index: entries match the rest of the patch
* record with each substring its source location to be able to make
  even more precise diagnostics
* check wether CONFIG* override match, e.g. CONFIGURE_DIRS most likely
  needs matching CNOFIG_GUESS_OVERRIDE and CONFIG_SUB_OVERRIDE as well