Escaped Name

Currently we store both the escaped and unescaped name in a Key and in a way that there cannot be an optimization not to store it (there are functions handling out the pointer).

• allow implementations of Elektra to not store two names

• the memory consumption of storing the name twice is considerable

• store it twice
• store it once but in one memory block

Remove the escaped name from struct _Key and use it only when necessary.

Clarify and reduce terminology.

API Changes:

• keyName returns the unescaped name (temporary some other name for PR: keyUnescapedName(Size))
• remove keyUnescapedName, keyGetUnescapedNameSize.
• reverse terminology: with "key name" we will refer to the unescaped (base) name, the escaped name will be explicitly called "escaped key name".
• escaped name will be only present in
  • keyNew (+ arguments for adding key names) [unclear: maybe not needed]
  • elektraEscapeName (operating on chars)
  • rename keyAddName, e.g. to keyAddEscapedName
• keyDup(.., int) with options to filter which parts are copied (to allow copy of keys where only the key name is copied)

• needs fix of OPMPHM
• Later modifications in keyNew to also accept key base names might be useful:
• keyNew(KEY_VALUE, "...", KEY_NAME, "", "...", KEY_END)
• keyNew (KEY_NAME, KEY_NS_USER, "abc", "def", KEY_NAME_END, KEY_END);