fix Makefile chmod (644)
replace MD5SUM with HASH
add PKG_MIRROR_HASH when PKG_SOURCE_PROTO:=git

(PKG_SOURCE_PROTO:=svn tarballs are not reproducible for now)

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

Use stdlib.h for malloc(), getenv() and realloc(). Fixes the following
build failure:

unixos.c:42:14: error: conflicting types for 'malloc'
 extern char *malloc();
              ^
Makefile:168: recipe for target 'unixos.o' failed
make[3]: *** [unixos.o] Error 1

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

Signed-off-by: Dmitry V. Zimin <pfzim@mail.ru>