Remove `alloc_clear`

Use `xcalloc` instead.
Inline `alloc_tv` and `alloc_string_tv` in eval.c
Remove code and checks for unsupported systems.

Remove remnants of support for systems including
__EMX__, MSDOS, OS2, AMIGA and MORPHOS.
Call to list_append_dict cannot fail.

Clean up the use of list_append_dict and remove error checks.
Call to list_append_string cannot fail.

Clean up the use of list_append_string and remove error checks.
Remove useless modelines (pt2)
Use portable format specifiers: Case %ld - plain - sscanf.

Fix uses of plain "%ld" within sscanf():
- Replace "%ld" with "%" SCNd64.
- Create (int64_t) local variable and sscanf into that.
- Safely downcast into previous type (introduce assertion, to be removed
  when variable type refactored).
Fix garray.* according to -Wconversion
Use portable format specifiers: Clarify some casted expressions.

Though correct (to my understanding), some of the casts introduced in
previous commits could lead to confusion, by casting only the first
expression component instead of the whole expression.

This fixes that, parenthesizing casted expressions, except where
operator precedence rules make it unneccesary.
Use portable format specifiers: Improve arguments formatting.

At some places, printf-like function's arguments styling could be
improved to enhance readability.
vim-patch:7.4.264

Problem:  Can't define a function starting with "g:". Can't assign a
          funcref to a buffer-local variable.
Solution: Skip "g:" at the start of a function name.
          Don't check for colons when assigning to a variable.

https://code.google.com/p/vim/source/detail?r=00acac0af680c2d8c82db5258474b121a5908926