chore(cmat): remove legacy makefiles and empty dirs

Drop the old GCC 3.4.2 makefile/make.mk pairs from Ex11, Ex11bug and
SolutionEx11bug; CMake builds everything now. Also remove the VS build
artifacts (pelican.obj.enc, unsuccessfulbuild markers) and prune the
now-empty Debug, Release, Backup and x64 directories. Original copies
remain in 397/.

Co-authored-by: Qwen 3.8 27B <qwen3.8_27b-q3_k_xl@lmstudio.local>

cmat/Ex11/make.mk

@@ -1,2 +0,0 @@
-BASEOBJS = \
-	Light.o main.o Pelican.o PelicanTimer.o Pole.o Timer.o TimerSet.o 

cmat/Ex11/makefile

@@ -1,17 +0,0 @@
-COMPILER = gcc
-FLAGS =  
-INCLUDES = -I/usr/local/include/c++/3.4.2 -I../DOS_Unix
-ARCHIVES = -L/usr/local/lib/gcc/sparc-sun-solaris2.7/3.4.2 -L/usr/local/lib -L/usr/lib
-UNIX_OBJS = ../DOS_Unix/CursesObj.o  ../DOS_Unix/Keyboard_Unix.o  ../DOS_Unix/Screen_Unix.o 
-
-include make.mk
-
-.SUFFIXES: .cpp .o
-
-all: pelican 
-
-.cpp.o:
-	$(COMPILER) $(INCLUDES) -frepo -c $(FLAGS) $*.cpp 
-
-pelican : $(BASEOBJS)
-	$(COMPILER) $(ARCHIVES) -o pelican -lcurses $(BASEOBJS) $(UNIX_OBJS) -lcurses -lstdc++ -static