New timer implementation

This is first part of new softserial code. Main timer code is changed, changes to rest of code are kept to minimum.

macros for BASEPRI based synchronization are added to project (atomic.h)

TIMER_PERIOD fixed in pwm_rx.c

src/main/common/utils.h

@@ -0,0 +1,44 @@
+/*
+ * This file is part of Cleanflight.
+ *
+ * Cleanflight is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Cleanflight is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Cleanflight.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stddef.h>
+
+#define ARRAYLEN(x) (sizeof(x) / sizeof((x)[0]))
+
+/*
+http://resnet.uoregon.edu/~gurney_j/jmpc/bitwise.html
+*/
+#define BITCOUNT(x) (((BX_(x)+(BX_(x)>>4)) & 0x0F0F0F0F) % 255)
+#define BX_(x) ((x) - (((x)>>1)&0x77777777) - (((x)>>2)&0x33333333) - (((x)>>3)&0x11111111))
+
+#define UNUSED(x) (void)(x)
+
+#if 0
+// ISO C version, but no type checking
+#define container_of(ptr, type, member) \
+                      ((type *) ((char *)(ptr) - offsetof(type, member)))
+#else
+// non ISO variant from linux kernel; checks ptr type, but triggers 'ISO C forbids braced-groups within expressions [-Wpedantic]'
+//  __extension__ is here to disable this warning
+#define container_of(ptr, type, member)  __extension__ ({       \
+        const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
+        (type *)( (char *)__mptr - offsetof(type,member) );})
+
+
+#endif