pcre.nim: added pcre_free and removed hacks in nre and re.nim

lib/impure/nre.nim

@@ -442,7 +442,7 @@ proc extractOptions(pattern: string): tuple[pattern: string, flags: int, study:
 # }}}
 
 proc destroyRegex(pattern: Regex) =
-  pcre.free_substring(cast[cstring](pattern.pcreObj))
+  pcre.free(pattern.pcreObj)
   pattern.pcreObj = nil
   if pattern.pcreExtra != nil:
     pcre.free_study(pattern.pcreExtra)

lib/impure/re.nim

@@ -60,12 +60,9 @@ proc rawCompile(pattern: string, flags: cint): ptr Pcre =
     raiseInvalidRegex($msg & "\n" & pattern & "\n" & spaces(offset) & "^\n")
 
 proc finalizeRegEx(x: Regex) =
-  # XXX This is a hack, but PCRE does not export its "free" function properly.
+  pcre.free(x.h)
-  # Sigh. The hack relies on PCRE's implementation (see ``pcre_get.c``).
-  # Fortunately the implementation is unlikely to change.
-  pcre.free_substring(cast[cstring](x.h))
   if not isNil(x.e):
-    pcre.free_substring(cast[cstring](x.e))
+    pcre.free_study(x.e)
 
 proc re*(s: string, flags = {reStudy}): Regex =
   ## Constructor of regular expressions.

lib/wrappers/pcre.nim

@@ -341,6 +341,8 @@ proc compile2*(pattern: cstring,
                erroffset: ptr cint,
                tableptr: pointer): ptr Pcre
 
+proc free*(p: ptr Pcre)
+
 proc config*(what: cint,
              where: pointer): cint