convert STRING_NOTFOUND -> NODE_NOTFOUND in connectivity

The code was interchangably using the two anyway.

Change-Id: I4f3fe8f1d699a9725bbcce0138a9d978a1eff28a
convert STRING_NOTFOUND -> -1 in editeng

And convert some xub_StrLen to sal_Int32 in the same patch of code.

Change-Id: I72c92bf9413dbca14688cb8d46a023df49a5d41a
convert STRING_NOTFOUND in sc module

ScGlobal::FindUnquoted
  - return -1 instead of STRING_NOTFOUND
  - change return type from xub_StrLen to sal_Int32
  - remove last two parameters because noone was using them

ScCompiler::GetDocTabPos
  - return -1 instead of STRING_NOTFOUND
  - change return type from xub_StrLen to sal_Int32

inputhdl.cxx/lcl_MatchParenthesis
  - return -1 instead of STRING_NOTFOUND
  - change return type from xub_StrLen to sal_Int32
  - make function static, no-one outside this module is using it

Change-Id: I141ab082db180ff2da5a7ca6813cd3607b9ea7f7