[DEBUG-ONLY] Bump initial condition handler stack size to avoid neste…

…d malloc issues

* We had an in-house test failure on an ARMV6L box with the following diff.

  ```diff
   > ideminter_rolrec_0/mupipstop_rollback_or_recover/impjob_imptp0.mje5
   > %YDB-F-ASSERT, Assert failed in sr_port/gtm_malloc_src.h line 695 for expression (FALSE)
   ```

  Below is the C-stack at the time of the assert failure.

  ```gdb
  #0  __pthread_kill () at ../sysdeps/unix/sysv/linux/pthread_kill.c:56
  #1  gtm_dump_core () at sr_unix/gtm_dump_core.c:74
  #2  ch_cond_core () at sr_unix/ch_cond_core.c:77
  #3  rts_error_va () at sr_unix/rts_error.c:192
  #4  rts_error_csa () at sr_unix/rts_error.c:99
  #5  gtm_malloc () at sr_port/gtm_malloc_src.h:695
  #6  condstk_expand () at sr_unix/condstk_expand.c:53
  #7  ydb_stm_invoke_deferred_signal_handler () at sr_unix/ydb_stm_invoke_deferred_signal_handler.c:59
  #8  deferred_signal_handler () at sr_port/deferred_signal_handler.c:57
  #9  gtm_malloc () at sr_port/gtm_malloc_src.h:748
  #10 iorm_use () at sr_unix/iorm_use.c:988
  #11 iorm_open () at sr_unix/iorm_open.c:254
  #12 io_open_try () at sr_unix/io_open_try.c:616
  #13 op_open () at sr_port/op_open.c:160
  #14 open_source_file () at sr_unix/source_file.c:253
  #15 compiler_startup () at sr_port/compiler_startup.c:130
  #16 compile_source_file () at sr_unix/source_file.c:173
  #17 op_zcompile () at sr_port/op_zcompile.c:57
  #18 gtm_trigger_complink () at sr_unix/gtm_trigger.c:451
  #19 gtm_trigger () at sr_unix/gtm_trigger.c:551
  #20 gvtr_match_n_invoke () at sr_unix/gv_trigger.c:1683
  #21 gvcst_put2 () at sr_port/gvcst_put.c:2806
  #22 gvcst_put () at sr_port/gvcst_put.c:299
  #23 op_gvput () at sr_port/op_gvput.c:79
  #24 ydb_set_s () at sr_unix/ydb_set_s.c:137
  #25 ydb_set_st () at sr_unix/ydb_set_st.c:42
  #26 _cgo_d187034042ca_Cfunc_ydb_set_st () at cgo-gcc-prolog:170
  #27 runtime.asmcgocall () at /usr/lib/go-1.11/src/runtime/asm_arm.s:617
  ```

* The cause of the assert failure is a nested call to `gtm_malloc()` (frames 9 and 5 above).
  And the reason that nested call happened is because the initial allocation of the condition handler
  stack size of 5 was not enough when `sr_unix/ydb_stm_invoke_deferred_signal_handler.c` tried to
  do an ESTABLISH and add one more condition handler (at frame number 7). This is because the
  condition handler stack was already used up with the following handlers.

  ```gdb
  (gdb) p chnd[0].ch
  $14 = (void (*)()) 0xb62f4f70 <stop_image_conditional_core>
  (gdb) p chnd[1].ch
  $15 = (void (*)()) 0xb63b0f10 <ydb_simpleapi_ch>
  (gdb) p chnd[2].ch
  $16 = (void (*)()) 0xb67f1e0c <gtm_trigger_complink_ch>
  (gdb) p chnd[3].ch
  $17 = (void (*)()) 0xb69c45e8 <source_ch>
  (gdb) p chnd[4].ch
  $18 = (void (*)()) 0xb6ce211c <compiler_ch>
  ```

* The initial condition handler stack size (controlled by the `CONDSTK_INITIAL_INCR` macro) is currently
  set to 5 (last changed from 2 to 5 as part of GT.M V6.3-000) for DEBUG builds and set to 8 for
  PRO/Release builds.

* Due to YottaDB's use of SimpleAPI, this limit of 5 is clearly not enough (as shown by the above failure)
  so it is now being bumped to 8 for DEBUG and to 16 for PRO/Release builds (just to be safe).

sr_unix/errorsp.h

@@ -3,7 +3,7 @@
  * Copyright (c) 2001-2019 Fidelity National Information	*
  * Services, Inc. and/or its subsidiaries. All rights reserved.	*
  *								*
- * Copyright (c) 2017-2019 YottaDB LLC and/or its subsidiaries. *
+ * Copyright (c) 2017-2020 YottaDB LLC and/or its subsidiaries. *
  * All rights reserved.						*
  *								*
  *	This source code contains the intellectual property	*
@@ -50,10 +50,13 @@
  * in addition to the other handlers for each trigger frame, the maximums may need to be re-visited.
  */
 #ifdef DEBUG
-#  define CONDSTK_INITIAL_INCR	5	/* Lower initial limit for DEBUG to exercise extensions. Note that values below 5 cause
-					 * issues with nested malloc()s when using certain ydb_dbglvl values. */
+#  define CONDSTK_INITIAL_INCR	8	/* Lower initial limit for DEBUG to exercise condition handler stack extensions.
+					 * Note that even a value of 5 has been seen to cause issues with nested malloc()s
+					 * (see commit message for details on the failure which showed this possibility).
+					 * Hence setting this to 8 for DEBUG and bumping the initial limit to 16 for PRO builds.
+					 */
 #else
-#  define CONDSTK_INITIAL_INCR	8	/* Initial increment value used when expanding condition handler stack */
+#  define CONDSTK_INITIAL_INCR	16	/* Initial increment value used when expanding condition handler stack */
 #endif
 #define CONDSTK_MAX_INCR	128	/* Increment doubles each time expanded till hits this level */
 #define CONDSTK_MAX_STACK	512	/* Actual max is approx 504 due to arithmetic progression */