don't use pthreads by default

Makefile

@@ -22,22 +22,22 @@ CFLAGS  ?= -O2 -Wall
 INSTALL ?= install
 PREFIX  ?= /usr/local
 
-# Disable multi threading. This will make the program smaller and a tiny
-# bit easier on the system. It will make it slower in real time though,
-# as we can't read from the harddisk and calculate hashes simultaneously.
-#NO_THREADS = 1
+# Use multiple POSIX threads for calculating hashes. This should be slightly
+# faster. Much faster on systems with multiple CPUs and fast harddrives.
+#USE_PTHREADS = 1
 
-# Use the SHA1 implementation in the OpenSSL library
+# Use the SHA1 implementation in the OpenSSL library instead of compiling our
+# own.
 #USE_OPENSSL = 1
 
-# Disable support for long options. Will make the program smaller
-# and perhaps even more portable.
+# Disable support for long options. Will make the program smaller and perhaps
+# even more portable.
 #NO_LONG_OPTIONS = 1
 
-# Disable a redundent check to see if the amount of bytes read from files
-# while hashing matches the sum of reported file sizes. I've never seen
-# this fail. It will fail if you change files yet to be hashed while
-# mktorrent is running, but who'd want to do that?
+# Disable a redundent check to see if the amount of bytes read from files while
+# hashing matches the sum of reported file sizes. I've never seen this fail. It
+# will fail if you change files yet to be hashed while mktorrent is running,
+# but who'd want to do that?
 #NO_HASH_CHECK = 1
 
 # Set the number of microseconds mktorrent will wait between every progress
@@ -46,12 +46,12 @@ PREFIX  ?= /usr/local
 #PROGRESS_PERIOD = 200000
 
 # Maximum number of file descriptors mktorrent will open when scanning the
-# directory. Default is 100, but I have no idea what a sane default
-# for this value is, so your number is probably better.
+# directory. Default is 100, but I have no idea what a sane default for this
+# value is, so your number is probably better.
 #MAX_OPENFD = 100
 
-# Enable leftover debugging code.
-# Usually just spams you with lots of useless information.
+# Enable leftover debugging code.  Usually just spams you with lots of useless
+# information.
 #DEBUG = 1
 
 
@@ -65,10 +65,9 @@ SRCS    := ftw.c init.c sha1.c hash.c output.c main.c
 OBJS     = $(SRCS:.c=.o)
 LIBS    :=
 
-ifdef NO_THREADS
-DEFINES += -DNO_THREADS
-SRCS := $(SRCS:hash.c=simple_hash.c)
-else
+ifdef USE_PTHREADS
+DEFINES += -DUSE_PTHREADS
+SRCS := $(SRCS:hash.c=hash_pthreads.c)
 LIBS += -lpthread
 endif