pic32prog.inc.mk: add support for pic32prog flasher

https://github.com/sergev/pic32prog

For PICkit3 it requires having it with scripting mode firware.

Source
------

RIOT-OS#6092 (comment)

Author: cladmi

makefiles/tools/pic32prog.inc.mk

@@ -0,0 +1,42 @@
+# pic32prog flasher
+# =================
+#
+# https://github.com/sergev/pic32prog
+#
+# Allow flashing pic32 boards using:
+#  * Microchip PICkit2
+#  * Microchip PICkit3 with script firmware
+#
+#
+# PICkit-3
+# --------
+#
+# Changing the firmware to 'scripting mode'
+# Should be done from a Windows computer as described here
+#
+# http://ww1.microchip.com/downloads/en/DeviceDoc/PICkit3%20Programmer%20Application%20v3.10.zip
+#
+# ### Setup summary
+#
+# * Extract PICkit3 Programmer Application Setup v3.10.zip
+# * setup.exe
+# * Run PICkit3
+# * Tools/Download PICkit Operating System
+#   * Select C://Program Files/Microchip/PICkit3/PK3OSV020005.hex
+#
+
+PIC32PROG = $(RIOTTOOLS)/pic32prog/pic32prog
+
+FLASHFILE ?= $(HEXFILE)
+
+FLASHER ?= $(PIC32PROG)
+FFLAGS  ?= $(FLASHFILE)
+
+# No reset command
+RESET ?=
+RESET_FLAGS ?=
+
+# Compile pic32prog if using the one provided in RIOT
+ifeq ($(PIC32PROG),$(FLASHER))
+  FLASHDEPS += $(PIC32PROG)
+endif