git-compat-util.h: do not #include <sys/param.h> by default

Earlier we allowed platforms that lack <sys/param.h> not to include
the header file from git-compat-util.h; we have included this header
file since the early days back when we used MAXPATHLEN (which we no
longer use) and also depended on it slurping ULONG_MAX (which we get
by including stdint.h or inttypes.h these days).

It turns out that we can compile our modern codebase just file
without including it on many platforms (so far, Fedora, Debian,
Ubuntu, MinGW, Mac OS X, Cygwin, HP-Nonstop, QNX and z/OS are
reported to be OK).

Let's stop including it by default, and on platforms that need it to
be included, leave "make NEEDS_SYS_PARAM_H=YesPlease" as an escape
hatch and ask them to report to us, so that we can find out about
the real dependency and fix it in a more platform agnostic way.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -167,7 +167,9 @@ all::
 # Define NO_POLL if you do not have or don't want to use poll().
 # This also implies NO_SYS_POLL_H.
 #
-# Define NO_SYS_PARAM_H if you don't have sys/param.h.
+# Define NEEDS_SYS_PARAM_H if you need to include sys/param.h to compile,
+# *PLEASE* REPORT to git@vger.kernel.org if your platform needs this;
+# we want to know more about the issue.
 #
 # Define NO_PTHREADS if you do not have or do not want to use Pthreads.
 #
@@ -1747,8 +1749,8 @@ endif
 ifdef NO_SYS_POLL_H
 	BASIC_CFLAGS += -DNO_SYS_POLL_H
 endif
-ifdef NO_SYS_PARAM_H
-	BASIC_CFLAGS += -DNO_SYS_PARAM_H
+ifdef NEEDS_SYS_PARAM_H
+	BASIC_CFLAGS += -DNEEDS_SYS_PARAM_H
 endif
 ifdef NO_INTTYPES_H
 	BASIC_CFLAGS += -DNO_INTTYPES_H

configure.ac

@@ -699,12 +699,6 @@ AC_CHECK_HEADER([sys/poll.h],
 [NO_SYS_POLL_H=UnfortunatelyYes])
 GIT_CONF_SUBST([NO_SYS_POLL_H])
 #
-# Define NO_SYS_PARAM_H if you don't have sys/param.h
-AC_CHECK_HEADER([sys/param.h],
-[NO_SYS_PARAM_H=],
-[NO_SYS_PARAM_H=UnfortunatelyYes])
-GIT_CONF_SUBST([NO_SYS_PARAM_H])
-#
 # Define NO_INTTYPES_H if you don't have inttypes.h
 AC_CHECK_HEADER([inttypes.h],
 [NO_INTTYPES_H=],

git-compat-util.h

@@ -104,7 +104,7 @@
 #endif
 #include <errno.h>
 #include <limits.h>
-#ifndef NO_SYS_PARAM_H
+#ifdef NEEDS_SYS_PARAM_H
 #include <sys/param.h>
 #endif
 #include <sys/types.h>