CONFIG: add support for WM_COMPILE_OPTION='Dbg'

- uses '-g -DFULLDEBUG' (like Debug), but with -O3 (like Opt).

  This adds in debug symbols and FULLDEBUG code segments (good for
  code development) but retains -O3 optimizations and code paths and
  avoids the much slower -O0 associated with 'Debug'.

- add in central wmake/General/common/{c,c++}XXX tuning,
  which helps reduce the number of nearly identical files

ENH: add support for wmake -debug-Og

wmake/rules/General/Gcc/c

@@ -1,10 +1,16 @@
-SUFFIXES += .c
+#------------------------------------------------------------------------------
+# gcc compiler
+#------------------------------------------------------------------------------
+SUFFIXES   += .c
 
-cc          = gcc$(COMPILER_VERSION)
+cc         := gcc$(COMPILER_VERSION)
 
-cARCH       =
-cDBUG       =
-cOPT        = -O2
-cWARN       = -Wall
+cARCH      :=
+cDBUG      :=
+cOPT       := -O2
+cWARN      := -Wall
+
+# Tuning
+sinclude $(GENERAL_RULES)/common/c$(WM_COMPILE_OPTION)
 
 #------------------------------------------------------------------------------

wmake/rules/General/Gcc/c++

@@ -4,14 +4,14 @@
 #
 # NOTE if your system gcc is new enough can simply use c++14 too.
 #------------------------------------------------------------------------------
-SUFFIXES += .C .cc .cpp .cxx
+SUFFIXES   += .C .cc .cpp .cxx
 
-CC          = g++$(COMPILER_VERSION) -std=c++11
+CC         := g++$(COMPILER_VERSION) -std=c++11
 
-c++ARCH     =
-c++DBUG     =
-c++OPT      = -O2
-ptFLAGS     = -DNoRepository -ftemplate-depth-100
+c++ARCH    :=
+c++DBUG    :=
+c++OPT     := -O2
+ptFLAGS    := -DNoRepository -ftemplate-depth-100
 
 c++WARN     = \
     -Wall -Wextra -Wold-style-cast \
@@ -24,4 +24,7 @@ c++LESSWARN = \
     -Wno-deprecated-declarations \
     -fpermissive
 
+# Tuning
+sinclude $(GENERAL_RULES)/common/c++$(WM_COMPILE_OPTION)
+
 #------------------------------------------------------------------------------