internal: introduce new types to avoid unsigned int rollover and signed int overflow (#7216)

* framebuffer: avoid gluint overflow

GLuint was being initialized to -1 and rolling over to unsigned int max,
its defined behaviour but very unnecessery. add a bool and use it for
checking if allocated or not.

* opengl: avoid gluint rollover

-1 rolls over to unsigned int max, use 0xFF instead.

* core: big uint64_t to int type conversion

there were a few uint64_t to int implicit conversions overflowing int
and causing UB, make all monitor/workspaces/windows use the new
typedefs. also fix the various related 64 to 32 implicit conversions
going around found with -Wshorten-64-to-32

src/signal-safe.hpp

@@ -139,7 +139,7 @@ class BufFileWriter {
             abort();
         } else {
             close(pipefd[1]);
-            int  len;
+            long len;
             char readbuf[256];
             while ((len = read(pipefd[0], readbuf, 256)) > 0) {
                 write(readbuf, len);
@@ -155,7 +155,7 @@ class BufFileWriter {
     void flush() {
         size_t i = 0;
         while (i < m_writeBufPos) {
-            int written = ::write(m_fd, m_writeBuf + i, m_writeBufPos - i);
+            auto written = ::write(m_fd, m_writeBuf + i, m_writeBufPos - i);
             if (written <= 0) {
                 return;
             }