adb: win32: make adb_getenv() case-insensitive

adb_getenv() should be case-insensitive just like the real getenv() on
Windows.

Added a unittest for adb_getenv(). In the process, made adb_test link
with -municode so that the environment block is Unicode.

Move wmain() from main.cpp to sysdeps_win32.cpp so that adb_test could
also use it.

Because wmain() moved, it wasn't as easy to do the runtime check to
verify that -municode was used, so do that check in _ensure_env_setup()
since adb_getenv() is called early in adb anyway.

Added a utility ToLower() which is good enough for env vars whose keys
are probably always ASCII to begin with.

Change-Id: I082f7fdee9dfe2c7f76b878528d2f7863df6d8d1
Signed-off-by: Spencer Low <CompareAndSwap@gmail.com>
4 files changed