Avoids a potentially uninitialized variable warning.

This patch removes the so called local variables defined per
file basis for certain editors to properly show tab width, and
similar settings. These are mainly used by Vim and Emacs editors
yet with recent changes the once working definitions don't work
anymore in Vim without custom plugins or additional configuration.
Neither are these settings synced across the PHP code base.

A simpler and better approach is EditorConfig and fixing code
using some code style fixing tools in the future instead.

This patch also removes the so called modelines for Vim. Modelines
allow Vim editor specifically to set some editor configuration such as
syntax highlighting, indentation style and tab width to be set in the
first line or the last 5 lines per file basis. Since the php test
files have syntax highlighting already set in most editors properly and
EditorConfig takes care of the indentation settings, this patch removes
these as well for the Vim 6.0 and newer versions.

With the removal of local variables for certain editors such as
Emacs and Vim, the footer is also probably not needed anymore when
creating extensions using ext_skel.php script.

Additionally, Vim modelines for setting php syntax and some editor
settings has been removed from some *.phpt files.  All these are
mostly not relevant for phpt files neither work properly in the
middle of the file.

While at it, also make sure that mbstring case conversion takes
into account the specified substitution character and substitution
mode.

Implement full case mapping according to SpecialCasing.txt and
also full case folding according to CaseFolding.txt (F). There
are a number of caveats:

* Only language-agnostic and unconditional full case mapping
  is implemented. The only language-agnostic conditional case
  mapping rule relates to Greek sigma in final position
  (Final_Sigma). Correctly handling this requires both arbitrary
  lookahead and lookbehind, which would require some larger
  changes to how the case mapping is implemented. This is a
  possible future extension.
* The only language-specific handling that is implemented is
  for Turkish dotted/undotted Is, if the ISO-8859-9 encoding
  is used. This matches the previous behavior and makes sure
  that no codepoints not supported by the encoding are
  produced. A future extension would be to also handle the
  Turkish mappings specified by SpecialCasing.txt based on
  the mbfl internal language.
* Full case folding is implemented, but case-insensitive mb_*
  operations continue to use simple case folding. The reason is
  that full case folding of the haystack string may change the
  position at which a match occurred. This would have to be
  mapped back into the position in the original string.
* mb_convert_case() exposes both the full and the simple case
  mapping / folding, where full is the default. The constants
  are:

   * MB_CASE_LOWER (used by mb_strtolower)
   * MB_CASE_UPPER (used by mb_strtolower)
   * MB_CASE_TITLE
   * MB_CASE_FOLD
   * MB_CASE_LOWER_SIMPLE
   * MB_CASE_UPPER_SIMPLE
   * MB_CASE_TITLE_SIMPLE
   * MB_CASE_FOLD_SIMPLE (used by case-insensitive operations)

Instead of using lowercasing.

Instead of performing a binary search, use a hashtable to store
the case maps. In particular a minimal perfect hash construction
is used, which does not require collision resolution (but does
use an auxiliary table for the hash perturbation).