DOC: assorted typo fixes in the documentation and Makefile

This is another round of cleanups in various docs and comments in the
Makefile.
diff --git a/Makefile b/Makefile
index 6c1d3ec..4c823fa 100644
--- a/Makefile
+++ b/Makefile
@@ -40,7 +40,7 @@
 #   USE_LUA              : enable Lua support.
 #   USE_FUTEX            : enable use of futex on kernel 2.6. Automatic.
 #   USE_ACCEPT4          : enable use of accept4() on linux. Automatic.
-#   USE_MY_ACCEPT4       : use own implemention of accept4() if glibc < 2.10.
+#   USE_MY_ACCEPT4       : use own implementation of accept4() if glibc < 2.10.
 #   USE_PRCTL            : enable use of prctl(). Automatic.
 #   USE_ZLIB             : enable zlib library support.
 #   USE_SLZ              : enable slz library instead of zlib (pick at most one).
@@ -141,7 +141,7 @@
 DOCDIR = $(PREFIX)/doc/haproxy
 
 #### TARGET system
-# Use TARGET=<target_name> to optimize for a specifc target OS among the
+# Use TARGET=<target_name> to optimize for a specific target OS among the
 # following list (use the default "generic" if uncertain) :
 #    linux-glibc, linux-glibc-legacy, solaris, freebsd, openbsd, netbsd,
 #    cygwin, haiku, aix51, aix52, aix72-gcc, osx, generic, custom
@@ -246,7 +246,7 @@
 # It's automatically appended depending on the targets.
 EXTRA =
 
-#### CPU dependant optimizations
+#### CPU dependent optimizations
 # Some CFLAGS are set by default depending on the target CPU. Those flags only
 # feed CPU_CFLAGS, which in turn feed CFLAGS, so it is not mandatory to use
 # them. You should not have to change these options. Better use CPU_CFLAGS or
@@ -260,7 +260,7 @@
 CPU_CFLAGS.power9     = -O2 -mcpu=power9 -mtune=power9
 CPU_CFLAGS            = $(CPU_CFLAGS.$(CPU))
 
-#### ARCH dependant flags, may be overridden by CPU flags
+#### ARCH dependent flags, may be overridden by CPU flags
 ARCH_FLAGS.32     = -m32
 ARCH_FLAGS.64     = -m64
 ARCH_FLAGS.i386   = -m32 -march=i386