Fix some build problems on MacOS X.

- Linking shared libraries needs slightly different options.

- We were trying to detect mach_time.h but needed to detect
  mach/mach_time.h instead.

While we're here, add a --disable-shared option to ./configure, which
is different from --enable-static.  --disable-shared does not build
*new* share libraries, but doesn't pass -static to the linker
(apparently there is no static linking posible on MacOS).

docs/cookbook/c/all.rc.od

@@ -10,7 +10,7 @@ rc_include \
 	rc/rt.autolib.rc \
 	rc/libpng.rc \
 	rc/clock_gettime.rc \
-	rc/mach_time.h.rc \
+	rc/mach__mach_time.h.rc \
 	rc/windows.h.rc \
 	rc/posix.rc \
 	rc/printf_lld.rc \

docs/cookbook/c/monotime.c

@@ -23,7 +23,7 @@ long long monotime(void) {
 	return !result ? 1 : result;
 }
 
-#elif HAVE_MACH_TIME_H
+#elif HAVE_MACH__MACH_TIME_H
 
 #include <mach/mach.h>
 #include <mach/mach_time.h>

docs/cookbook/c/rc/posix.rc.od

@@ -8,13 +8,13 @@ struct timespec x;
 '
 
 x=
-rc_replaceln HAS_POSIX 1
+rc_replaceln HAVE_POSIX 1
 if ! rc_compile cc link "$prog"; then
 	x="-D_XOPEN_SOURCE=500"
 	rc_appendln CPPFLAGS "$x"
 	if ! rc_compile cc link "$prog"; then
 		rc_undo
-		rc_replaceln HAS_POSIX ""
+		rc_replaceln HAVE_POSIX ""
 	fi
 fi
 rc_save

redoconf/configure.sh

@@ -50,7 +50,8 @@ usage() {
 
     --prefix=       Change installation prefix (usually /usr/local)
     --host=         Architecture prefix for output (eg. i686-w64-mingw32-)
-    --enable-static               Link libraries and binaries statically
+    --enable-static               Link binaries statically
+    --disable-shared              Do not build shared libraries
     --{dis,en}able-optimization   Disable/enable optimization for C/C++
     --{dis,en}able-debug          Disable/enable debugging flags for C/C++
     -h, --help      This help message
@@ -115,6 +116,9 @@ for d in "$@"; do
 		--enable-static)
 			emit "STATIC" "1"
 			;;
+		--disable-shared)
+			emit "NOSHARED" "1"
+			;;
 		--enable-optimization)
 			emit_append OPTFLAGS "-O2"
 			;;

redoconf/link-shlib.od

@@ -2,7 +2,7 @@
 rc_include _all.rc rc/shlib.rc
 
 # Tricky quoting: see _compile.od for details.
-if [ "$HAVE_SHLIB" = 1 ]; then
+if [ "$HAVE_SHLIB" = UNIX ]; then
 	cat >$3 <<-EOF
 		#!/bin/sh -e
 		LINK=$(shquote "$LINK")
@@ -20,6 +20,25 @@ if [ "$HAVE_SHLIB" = 1 ]; then
 		  "\$@" \\
 		  \$LIBS
 	EOF
+elif [ "$HAVE_SHLIB" = MACOS ]; then
+	cat >$3 <<-EOF
+		#!/bin/sh -e
+		LINK=$(shquote "$LINK")
+		LDFLAGS=$(shquote "$LDFLAGS")
+		OPTFLAGS=$(shquote "$OPTFLAGS")
+		LIBS=$(shquote "$LIBS")
+		LIBDIR=$(shquote "$LIBDIR")
+		o="\$1"
+		ob="\${o#*/}"
+		shift
+		IFS="$NL"
+		set -f
+		\$LINK -dynamiclib -o "\$o" \\
+		  -install_name "\$ob" \\
+		  \$LDFLAGS \$OPTFLAGS \\
+		  "\$@" \\
+		  \$LIBS
+	EOF
 else
 	# If no shared library support and we try to build one,
 	# compensate by building a static library instead in the

redoconf/rc/default.h.rc.od

@@ -2,8 +2,9 @@
 rc_include rc/CC.rc
 
 base="${1#*/}"
-h="${base%.rc}"
+h1="${base%.rc}"
-H=$(echo "$h" | tr 'a-z.' 'A-Z_')
+h=$(echo "$h1" | sed -e 's,__,/,g')  # x__y_z.h.rc.od -> <x/y_z.h>
+H=$(echo "$h1" | tr 'a-z.' 'A-Z_')
 
 if rc_compile cc nolink "#include <$h>"; then
 	rc_replaceln "HAVE_$H" 1

redoconf/rc/shlib.rc.od

@@ -1,21 +1,43 @@
 . ./redoconf.rc
 rc_include rc/CC.rc
 
-appendln CFLAGS "-fPIC"
-appendln LDFLAGS "-shared"
-
 prog='
 #include <stdlib.h>
 void f() { atoi(""); }
 '
 
+try_unix_style() {
+	(
+		appendln CFLAGS "-fPIC"
+		appendln LDFLAGS "-shared"
+		appendln LDFLAGS "-Wl,-soname,x.so"
+		RCC_NO_MAIN=1 rc_compile cc link "$prog"
+	)
+}
+
+try_macos_style() {
+	(
+		appendln CFLAGS "-fPIC"
+		appendln LDFLAGS "-dynamiclib"
+		appendln LDFLAGS "-current_version"
+		appendln LDFLAGS "1.0"
+		RCC_NO_MAIN=1 rc_compile cc link "$prog"
+	)
+}
+
 if [ -n "$STATIC" ]; then
 	echo "--enable-static specified; not building shared libraries." >&2
 	rc_replaceln HAVE_SHLIB ""
-elif RCC_NO_MAIN=1 rc_compile cc link "$prog"; then
+elif [ -n "$NOSHARED" ]; then
-	rc_replaceln HAVE_SHLIB 1
+	echo "--disable-shared specified; not building shared libraries." >&2
+	rc_replaceln HAVE_SHLIB ""
+elif try_unix_style; then
+	rc_replaceln HAVE_SHLIB UNIX
+elif try_macos_style; then
+	rc_replaceln HAVE_SHLIB MACOS
 else
 	echo "Not building shared libraries on this platform." >&2
+	rc_undo
 	rc_replaceln HAVE_SHLIB ""
 fi
 rc_save