cfg.mk: Use single quotes wherever possible

Being consistent is nice, especially when it comes to defining our
regular expression, where using single quotes instead of double
quotes allows us to leave out a few backslashes.

Changing this required altering a few error messages.

The only remaining use of double quotes is one where they are
actually required for the check to work.

cfg.mk

@@ -454,20 +454,20 @@ sc_prohibit_nonreentrant:
 	exit $$fail
 
 sc_prohibit_select:
-	@prohibit="\\<select *\\("					\
-	halt="use poll(), not se""lect()"				\
+	@prohibit='\<select *\('					\
+	halt='use poll(), not se''lect()'				\
 	  $(_sc_search_regexp)
 
 # Prohibit the inclusion of <ctype.h>.
 sc_prohibit_ctype_h:
 	@prohibit='^# *include  *<ctype\.h>'				\
-	halt="don't use ctype.h; instead, use c-ctype.h"		\
+	halt='use c-ctype.h instead of ctype.h'				\
 	  $(_sc_search_regexp)
 
 # Insist on correct types for [pug]id.
 sc_correct_id_types:
 	@prohibit='\<(int|long) *[pug]id\>'				\
-	halt="use pid_t for pid, uid_t for uid, gid_t for gid"		\
+	halt='use pid_t for pid, uid_t for uid, gid_t for gid'		\
 	  $(_sc_search_regexp)
 
 # "const fooPtr a" is the same as "foo * const a", even though it is
@@ -503,12 +503,12 @@ ctype_re = isalnum|isalpha|isascii|isblank|iscntrl|isdigit|isgraph|islower\
 
 sc_avoid_ctype_macros:
 	@prohibit='\b($(ctype_re)) *\('					\
-	halt="don't use ctype macros (use c-ctype.h)"			\
+	halt='use c-ctype.h instead of ctype macros'			\
 	  $(_sc_search_regexp)
 
 sc_avoid_strcase:
 	@prohibit='\bstrn?case(cmp|str) *\('				\
-	halt="don't use raw strcase functions (use c-strcase instead)"	\
+	halt='use c-strcase.h instead of raw strcase functions'		\
 	  $(_sc_search_regexp)
 
 sc_prohibit_virBufferAdd_with_string_literal:
@@ -810,7 +810,7 @@ sc_require_enum_last_marker:
 sc_prohibit_semicolon_at_eol_in_python:
 	@prohibit='^[^#].*\;$$'			                        \
 	in_vc_files='\.py$$'						\
-	halt="Don't use semicolon at eol in python files"		\
+	halt='python does not require to end lines with a semicolon'	\
 	  $(_sc_search_regexp)
 
 # mymain() in test files should use return, not exit, for nicer output
@@ -917,7 +917,7 @@ sc_prohibit_virConnectOpen_in_virsh:
 sc_require_space_before_label:
 	@prohibit='^(   ?)?[_a-zA-Z0-9]+:$$'                           \
 	in_vc_files='\.[ch]$$'                                         \
-	halt="Top-level labels should be indented by one space"        \
+	halt='Top-level labels should be indented by one space'        \
 	  $(_sc_search_regexp)
 
 # Allow for up to three spaces before the label: this is to avoid running
@@ -926,14 +926,14 @@ sc_require_space_before_label:
 sc_prohibit_space_in_label:
 	@prohibit='^ {0,3}[_a-zA-Z0-9]+ +:$$'                          \
 	in_vc_files='\.[ch]$$'                                         \
-	halt="There should be no space between label name and colon"   \
+	halt='There should be no space between label name and colon'   \
 	  $(_sc_search_regexp)
 
 # Doesn't catch all cases of mismatched braces across if-else, but it helps
 sc_require_if_else_matching_braces:
 	@prohibit='(  else( if .*\))? {|} else( if .*\))?$$)'		\
 	in_vc_files='\.[chx]$$'						\
-	halt="if one side of if-else uses {}, both sides must use it"	\
+	halt='if one side of if-else uses {}, both sides must use it'	\
 	  $(_sc_search_regexp)
 
 sc_curly_braces_style:
@@ -993,7 +993,7 @@ sc_prohibit_static_zero_init:
 sc_prohibit_devname:
 	@prohibit='\bdevname\b'	\
 	exclude='sc_prohibit_devname' \
-	halt='avoid using 'devname' as FreeBSD exports the symbol' \
+	halt='avoid using devname as FreeBSD exports the symbol' \
 	  $(_sc_search_regexp)
 
 sc_prohibit_system_error_with_vir_err:
@@ -1007,7 +1007,7 @@ sc_prohibit_system_error_with_vir_err:
 sc_prohibit_virXXXFree:
 	@prohibit='\bvir(Domain|Network|NodeDevice|StorageVol|StoragePool|Stream|Secret|NWFilter|Interface|DomainSnapshot)Free\b'	\
 	exclude='sc_prohibit_virXXXFree' \
-	halt='avoid using 'virXXXFree', use 'virObjectUnref' instead' \
+	halt='avoid using virXXXFree, use virObjectUnref instead' \
 	  $(_sc_search_regexp)
 
 sc_prohibit_sysconf_pagesize:
@@ -1018,7 +1018,7 @@ sc_prohibit_sysconf_pagesize:
 sc_prohibit_pthread_create:
 	@prohibit='\bpthread_create\b' \
 	exclude='sc_prohibit_pthread_create' \
-	halt="avoid using 'pthread_create', use 'virThreadCreate' instead" \
+	halt='avoid using pthread_create, use virThreadCreate instead' \
 	  $(_sc_search_regexp)
 
 sc_prohibit_not_streq: