Minor optimisations and bug fixes

Fix bug in mt_mpmc.c, in Linux mutexes are not recursive.
Add arena_trim_string() to the arena API
Removing arena->path, now paths are pushed to arena->metadata
Replacing fe->owner[128] with char *owner; the owner is not pushed as a
string to arena->metadata and trimed with arena_trim_string()
Improving cache locality in arena->metadata, the memory layout is not
fe; fe->path; fe->owner.
Cache aligning all arenas except HasherContext->arena to sizeof(void *).
Pushing elements one by one instead of snprintf() in finalize_file() and
hash_worker().
Getting the full path of current directory instead of "."
Fixing bug in path formating, this allow us to remove normalize_path()
from the hot loop.

build.bat

@@ -1,6 +1,8 @@
 @echo off
 setlocal enabledelayedexpansion
 
+set PROJECT_NAME=filehasher
+
 :: ============================================================================
 :: build.bat
 :: ============================================================================
@@ -45,7 +47,7 @@ exit /b 1
 :main
 set BUILD_DIR=%SCRIPT_DIR%\build\windows\%BUILD_TYPE%
 
-echo === Building filehasher (%BUILD_TYPE%) ===
+echo === Building %PROJECT_NAME% (%BUILD_TYPE%) ===
 
 :: --------------------------------------------------------------------------
 :: Clean if requested
@@ -167,4 +169,4 @@ popd
 
 echo.
 echo === Build Complete ===
-echo Executable: %BUILD_DIR%\filehasher.exe
+echo Executable: %BUILD_DIR%\%PROJECT_NAME%.exe