seqalign.hpp: add member initializers to AlignmentScoring (C++14)

Let's try if the first C++14 feature in the library works for everyone

The initializers were discussed in #302:
#302 (comment)

.github/workflows/ci.yml

@@ -188,7 +188,7 @@ jobs:
     env:
       CC: clang-8
       CXX: clang++-8
-      SKBUILD_CMAKE_ARGS: "-DCMAKE_CXX_STANDARD=11;-DEXTRA_WARNINGS=ON;-DSTANDALONE_PYTHON_MODULE=OFF"
+      SKBUILD_CMAKE_ARGS: "-DEXTRA_WARNINGS=ON;-DSTANDALONE_PYTHON_MODULE=OFF"
       SKBUILD_CMAKE_TARGETS: "all;check"
     steps:
     - uses: actions/checkout@v4

CMakeLists.txt

@@ -208,7 +208,7 @@ add_library(gemmi::headers ALIAS gemmi_headers)
 target_include_directories(gemmi_headers INTERFACE
     "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>"
     "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>")
-target_compile_features(gemmi_headers INTERFACE cxx_std_11)
+target_compile_features(gemmi_headers INTERFACE cxx_std_14)
 set_target_properties(gemmi_headers PROPERTIES EXPORT_NAME headers)
 
 add_library(gemmi_cpp

include/gemmi/seqalign.hpp

@@ -18,18 +18,18 @@
 namespace gemmi {
 
 struct AlignmentScoring {
-  int match;
-  int mismatch;
-  int gapo;  // gap opening penalty
-  int gape;  // gap extension penalty
+  int match = 1;
+  int mismatch = -1;
+  int gapo = -1;  // gap opening penalty
+  int gape = -1;  // gap extension penalty
   // In a polymer in model, coordinates are used to determine expected gaps.
-  int good_gapo;  // gap opening in expected place in a polymer
-  int bad_gapo;  // gap opening that was not predicted
+  int good_gapo = 0;  // gap opening in expected place in a polymer
+  int bad_gapo = -2;  // gap opening that was not predicted
   std::vector<std::int8_t> score_matrix;
   std::vector<std::string> matrix_encoding;
 
   static const AlignmentScoring* simple() {
-    static const AlignmentScoring s = { 1, -1, -1, -1, 0, -2, {}, {} };
+    static const AlignmentScoring s;
     return &s;
   }
   // Scoring for alignment of partially-modelled polymer to its full sequence