Separate htoprc for htop and pcp-htop to prevent overwrite

The original intention with pcp-htop was to share the same
htoprc configuration file with regular htop.  However this
also stores tab configuration which causes confusion since
the default pcp-htop tab set is unintentionally reduced to
match the defaults on Linux (when htop is invoked prior to
pcp-htop).

Relates to issue #952.
diff --git a/configure.ac b/configure.ac
index b1e2e9c..dfa3e29 100644
--- a/configure.ac
+++ b/configure.ac
@@ -599,6 +599,19 @@
 fi
 AC_DEFINE_UNQUOTED([OSRELEASEFILE], ["$with_os_release"], [File with OS release details.])
 
+AC_ARG_WITH([config],
+            [AS_HELP_STRING([--with-config=DIR],
+			    [configuration path @<:@default=/.config@:>@])],
+            [],
+            [with_config="/.config"])
+dnl Performance Co-Pilot configuration location to prevent overwrite
+if test "$my_htop_platform" = pcp -a "$with_config" = /.config; then
+    with_config="/.pcp"
+elif test -z "$with_config"; then
+   AC_MSG_ERROR([bad empty value for --with-config option])
+fi
+AC_DEFINE_UNQUOTED([CONFIGDIR], ["$with_config"], [Configuration path.])
+
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